MIDM K 3.0 Pro vs Claude Opus 5.5: A 20× Price Gap and One Scored Model

Take a 40,000-token input and ask for 2,000 tokens back. On Mi:dm K 3.0 Pro — MIDM K 3.0 Pro in catalogue spelling, the model KT released on 29 October 2026 — that request bills at eight thousandths of a cent in and sixteen ten-thousandths out, $0.0096 in total. On Claude Opus 5.5, which A​nthropic released on 22 September 2026, the same request bills at $0.16 in and $0.04 out, $0.20 in total. Run it a million times: $9,600 against $200,000. That is the whole comparison in one multiplication, and it is why the matchup gets typed into a search box at all. The harder question is what the extra $190,400 buys, and the answer to that is more concrete than a price ratio — because one of these two models has an independent score and a published benchmark sheet, and the other has neither.

What is actually known about each, side by side

• Status — Claude Opus 5.5 has been generally available since 22 September 2026 on A​nthropic's own API, with a retirement commitment of not sooner than 22 September 2027. Mi:dm K 3.0 Pro became billable on KT's Token Factory platform on 29 October 2026 and appeared on international catalogues on 5 November, six days before this page.

• Price per million tokens — Claude Opus 5.5 is $4.00 input and $20.00 output. Mi:dm K 3.0 Pro is $0.20 and $0.80. The ratio is 20× on input and 25× on output.

• Cache pricing — Opus 5.5 reads cached input at $0.20 per million and writes at $5.00, so a warm prompt costs a twentieth of a cold one. Mi:dm K 3.0 Pro reads cache at $0.04 and lists the same rate for cache writes; KT's own platform currently discounts all four lines by 30%.

• Context window — 1,000,000 tokens for Claude Opus 5.5 against 261,795 for Mi:dm K 3.0 Pro. Nearly a four-to-one gap, and the one spec difference that changes what a workload can be rather than how much it costs.

• Maximum output — 128,000 tokens for Opus 5.5 in the synchronous API, rising to 300,000 behind a beta header on the Batches API. Mi:dm K 3.0 Pro returns up to 235,615 tokens, which is the larger figure of the two.

• Input modality — Opus 5.5 takes text, images and files. Mi:dm K 3.0 Pro takes text only.

• Architecture — A​nthropic does not publish parameter counts. KT publishes its own: 120 billion total parameters, 12 billion active per token, in a stack that mixes Mamba, mixture-of-experts and attention layers, served from a checkpoint with NVFP4 experts and FP8 projections.

• Reasoning control — both expose one, and they work differently. Opus 5.5 has adaptive thinking that cannot be disabled, with effort as the only lever and a default of medium. Mi:dm K 3.0 Pro exposes a reasoning flag and returns the trace separately, with no vendor-published effort ladder.

• Tool calling — Opus 5.5 lists tools and tool_choice among its supported request parameters. Mi:dm K 3.0 Pro's catalogue entry does not, so function calling is unverified rather than supported or refused.

• Independent evaluation — Artificial Analysis scores Claude Opus 5.5 at 58 on its Intelligence Index, first of the models it ranks. It has no entry for Mi:dm K 3.0 Pro at all.

The one number that decides this matchup

Artificial Analysis puts Claude Opus 5.5 at 58 on its Intelligence Index and at $5.98 to run the full index suite once. Both figures are independent measurements of a shipped model, run through a fixed harness, which makes them comparable to other entries on the same index rather than to a vendor's own chart.

For Mi:dm K 3.0 Pro there is no entry, no score, and no per-task cost, because the model has not been run through that harness. That absence is not a neutral fact. It means every claim about the model's capability in this matchup is an inference from architecture and price, and a 120B mixture of experts with 12B active that costs a fifth of D​eepSeek's flagship is not, on architecture alone, a model anyone should expect to sit near 58.

To be fair to KT, part of the reason is timing. A model that has been billable for thirteen days and internationally listed for six has had no window in which an evaluator would have published. The absence of a score in week two says nothing about where the score will land. What it does say is that the 20× discount is currently unpriced risk rather than a measured efficiency, and a buyer who treats it as the latter is guessing.

Where the price gap stops being the interesting number

Twenty times is a large multiplier, and it is easy to stop there. Three things make the comparison more interesting than the ratio.

The first is context. Opus 5.5 reads a million tokens; Mi:dm K 3.0 Pro reads 262K. For a retrieval pipeline that stuffs 300K tokens of documents into a prompt, the cheap model is not a cheaper option — it is not an option. The gap is architectural, and no amount of prompt engineering closes a 738,000-token deficit.

The second is modality. Opus 5.5 accepts images and files. A workload that involves reading a scanned invoice, a screenshot of a failing test, or a PDF deck cannot be moved to a text-only model without a separate extraction stage, and that stage costs money and adds a failure mode. On document-heavy work the true comparison is not $0.20 against $4.00; it is $0.20 plus an OCR pipeline and its error rate against $4.00.

The third is the effort setting, and it is the one most comparisons miss. Opus 5.5's published scores are produced at max effort by default with named exceptions — Terminal-Bench 4.0 at xhigh, FrontierCode and CursorBench at the medium default — so the 58 is closer to a ceiling than to a routine run. A cheaper configuration exists on the same model, and the bill follows it. If your workload sits at low effort, the effective gap to a $4 model is smaller than the rate card implies, because you are not buying the configuration the headline score describes.

The cache line is where a cheap model stops being cheap

Long-agent workloads rarely send the same prompt once. They send a large fixed prefix — system prompt, tool definitions, repository context — hundreds of times, and the cache line is what decides the bill.

Opus 5.5 charges $0.20 per million tokens to read cached input, a twentieth of its base rate, with a 512-token minimum for cacheability. Mi:dm K 3.0 Pro charges $0.04 at list, which is also a fifth of its base rate. The ratio between the two models stays at 5× on cached input rather than 20× on fresh input, because Opus's cache discount is deeper in absolute terms.

That is the useful correction to the headline. On a workload with a 90% cache hit rate — a long-running coding agent, say — the blended input cost is not twenty times cheaper on the Korean model. It is closer to five. And if KT's 30% promotional discount ends while A​nthropic's cache rate holds, the gap narrows further. Anyone modelling a migration from the rate card's first two numbers should re-run it on a cache-weighted blend before believing the 20×.

What Opus 5.5 is actually selling at that price

Three published capabilities explain the premium better than a parameter count does.

Long-horizon agentic work is the first. A​nthropic's own model picker directs most workloads to Opus 5.5 and sends only the hardest long-horizon cases up to Claude Fable 5.1, which is the company saying that this model is the default for multi-step work rather than a specialist. A model positioned as the default has been tested against the failures that make agents unreliable, and those failures — losing the thread at step forty, dropping a tool result, repeating a completed edit — are not visible in a spec sheet.

Effort as a behavioural control is the second. Opus 5.5 steers the whole response, thinking included, with a single parameter, and A​nthropic documents it as a behavioural signal rather than a token budget. That gives a team a way to buy back cost on easy traffic without changing models, which is precisely the lever a cheap alternative is supposed to provide — except here it is available on the expensive model too.

Operational guarantees are the third, and they are dull in a way that matters. A published retirement floor two years out, a batch tier at 50% off both directions, a documented cache hierarchy with 5-minute and 1-hour write prices, and a US-only inference option carrying a 1.1× multiplier. None of that is capability. All of it is the difference between a model you can put in a contract and one you cannot.

Where Mi:dm K 3.0 Pro earns its place

The case for the Korean model is not that it is nearly as good for a fifth of the price. Nobody has shown that. The case is narrower and, for some teams, sufficient.

High-volume text classification, extraction and summarisation are the obvious fit. These are tasks where output is checked cheaply, errors are recoverable, and the same prompt runs millions of times. At $0.20 in and $0.80 out, a million-document extraction job that would bill six figures on Opus 5.5 bills four on Mi:dm K 3.0 Pro, and if the extraction accuracy holds at 97% instead of 99%, the arithmetic can still favour the cheap model — because the 2% difference is caught by a validation layer that costs less than the difference in inference.

Korean-language work is the second fit, and it is the one the model was built for. KT's Mi:dm line has been positioned since Mi:dm 2.0 as a Korea-centric family tuned for domestic vocabulary, culture and domain text, and a 120B model from that programme is a different proposition on Korean customer service transcripts than a frontier model with Korean competence as a secondary capability. That claim is testable in an afternoon and worth testing before it is believed.

Bulk, low-stakes generation is the third: drafts, variants, synthetic data for a filter you already trust. The cost of being wrong is one discarded sample.

What it is not for, on the evidence available: agentic coding against a large repository, anything that needs tool calling in a loop, anything with images or files, anything that needs more than 262K tokens of context, and anything where a wrong answer is expensive and unverifiable. Those are exactly the workloads Opus 5.5 is priced for, and the premium is doing real work in them.

Running both, and the failover difference

Claude Opus 5.5 is live on OrcaRouter as a​nthropic/claude-opus-5.5 at A​nthropic's list rate with no markup on top — $4.00 input, $20.00 output, $0.20 cache read, $5.00 cache write. Mi:dm K 3.0 Pro is not on our routes; it is served by KT alone, and a single-provider model is a single point of failure by construction.

That asymmetry is the practical argument for keeping both on one key rather than choosing. OrcaRouter's routing layer can hold Opus 5.5 as the path for hard requests and fall back to a cheaper model when a request fails or a budget threshold is crossed, and it does that across more than 200 models without a second contract or a code change. What it cannot do today is fail over to Mi:dm K 3.0 Pro, because there is one place to get it. The workable shape is therefore: the Korean model as a direct call for the bulk tier it is priced for, Opus 5.5 as the routed default for everything that matters, and a routing rule that keeps the second out of the first's failure path.

Cost is only half of what the routing decision is about. A cheap model with a 100% availability reading is measuring one endpoint, not a market; the reading is honest and it is also not a guarantee, because there is no second host to move to when it changes.

The short version

Claude Opus 5.5 is a measured model at a measured price: 58 on the independent index, first where it is ranked, a million tokens of context, multimodal input, tool calling, a published retirement floor and a rate card that has been stable since September. Mi:dm K 3.0 Pro is a cheaper model with a bigger output ceiling, a quarter of the context, no images, unverified tool use, one provider, and no public score of any kind.

Buy the Opus for the workloads where being wrong is expensive and the answer has to hold at step forty of an agent run. Test the Korean model on the workloads where volume dominates, output is checkable, and the language is Korean — the experiment costs cents per thousand documents and answers the only question this page cannot. Do not migrate a production path to a model that has been billable for thirteen days and independently evaluated zero times, however attractive the ratio looks on the rate card.