Guides / claude opus 4.8 pricing
Claude Opus 4.8 pricing, and why five versions cost the same
Claude Opus 4.8 pricing is $5.00 per million input tokens and $25.00 per million output tokens, and Opus 4.5, 4.6, 4.7 and the newer Opus 5 all bill identically. So an Opus version pin saves nothing at all. Culpa, a local-first LLM cost, margin, and forecast ledger, records the model version on every call, so a stale pin shows up as a fact.
Why this happens
Five Opus versions share one rate in this price book, Opus 4.5 through 4.8 plus Opus 5, which produces a specific and common waste. Teams pin an older Opus version to avoid the risk of a change, and assume the pin is also saving money. It isn't. The rate is identical, so the pin buys behavioural stability and nothing else. Meanwhile the older pin often carries older prompt habits, usually a fatter system prompt written for a model that needed more steering.
What this usually looks like
- Production is pinned to an Opus version from several releases ago and nobody remembers deciding that.
- The pin is justified as a cost measure, which the rate card doesn't support.
- Different services in the same product run different Opus versions, with no cost difference between them.
- The prompt attached to the older pin is noticeably longer than the one used elsewhere.
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Mistakes that cost the most
| Mistake | Why it hurts | Do instead |
|---|---|---|
| Keeping an older Opus pin to save money. | All five versions bill the same, so the pin costs the same and gives up whatever the newer version improved. | Decide the pin on behaviour alone, and re-test the newer version on your own evaluation set. |
| Carrying an old prompt forward across an Opus upgrade. | Prompts written for an older version often over-steer, and every extra token bills at $5 per million. | Re-test whether the extra steering is still needed, then trim what a newer version handles unprompted. |
| Running the whole agent loop on Opus because the reasoning step needs it. | Routing and formatting steps bill at $5 and $25 per million to do work a small model does identically. | Split the loop by step type and price each. This is usually the largest single saving on an agent. |
Run this check tonight
- List which Opus version each service pins, and confirm anyone can explain why.
- Check whether the pin was ever justified as a cost decision. If so, that reasoning was wrong.
- Compare the system prompt on your oldest pin against your newest. Price the difference at $5 per million.
- Count what share of your Opus calls are reasoning steps versus mechanical ones.
- Price the cache-write rate on your traffic. Opus cache writes bill at $6.25 per million, above the input rate.
Cache writes above the input rate, and what that means
Illustrative example
An Opus 4.8 workload sending a 6,000-token system prompt on every call, 200,000 calls a month. Rates from the price book: $5.00 input, $25.00 output, $0.50 cached read, and a five-minute cache write at $6.25 per million, derived at 1.25 times input.
Caching takes $5,400 a month off this prompt and clears break-even on the first read. Only a cache rebuilt with no read at all loses, and then by 25%.
Every number, with its confidence and source
| Figure | What it means | Confidence | Source |
|---|---|---|---|
| $5.00 / $25.00 per million | Claude Opus 4.5, 4.6, 4.7, 4.8 and Opus 5 input and output rates, identical across all five | calculated | Culpa price book rows for anthropic/claude-opus-4-5 through 4-8 and claude-opus-5, all $0.005 and $0.025 per 1k, verified against Anthropic pricing on 2026-08-01. |
| $6.25 per million | Opus five-minute cache write rate, above the input rate | calculated | $0.005 per 1k input x 1.25, the published Anthropic cache-write multiplier, mirrored from the ledger's own derivation in migration 0020. |
What a generic answer can’t know
A rate card can tell you five Opus versions cost the same. It can't tell you which version each of your services actually pinned, or that the oldest pin carries a prompt six hundred tokens longer than the rest. That needs per-call version and token data. Culpa records it on your infrastructure, keeps your prompts and responses there, and counts the calls to run your plan.
Questions founders ask next
Is Claude Opus 4.8 more expensive than Opus 4.5?
No. Opus 4.5, 4.6, 4.7, 4.8 and the newer Opus 5 all bill $5.00 per million input and $25.00 per million output. Choosing between them is a behaviour decision, never a cost one.
What does an Opus cache write cost?
$6.25 per million for the five-minute window and $10.00 for the one-hour window, derived at 1.25 and 2 times the $5.00 input rate. Both sit above the input rate, so a cache you rebuild too often costs more than not caching.
Should I run a whole agent on Opus?
Rarely. Planning and synthesis benefit from it. Tool selection, routing and formatting usually run identically on a model costing a fifth as much, and splitting the loop by step type is generally the biggest saving available.
On your infrastructure
Culpa runs on your infrastructure. Your prompts and responses never leave it. Culpa counts calls to run your plan, and it fails open, so if it ever breaks your app keeps running.
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Keep reading
Sources: Anthropic pricing. Last reviewed 2026-08-01, rates effective 2026-07-02. Plain text version.