Anthropic's and OpenAI's newest flagships both offer a 1M-token context window, but they price long prompts and cached context very differently. This page shows where that changes the bill, not just the headline rate.
Claude Opus 5.5 is cheaper on every metered line: $4.00 vs $10.00 input, $20.00 vs $50.00 output. The gap widens further on prompts above 272K tokens, where GPT-6 Astra moves to a higher rate and Opus 5.5 does not. Pick Astra for reasons other than price — an existing OpenAI stack, its tooling, or your own evals.
| Claude Opus 5.5 | GPT-6 Astra | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Tier | Flagship | Flagship |
| Input / 1M tokens | $4.00 | $10.00 |
| Output / 1M tokens | $20.00 | $50.00 |
| Cache hit / 1M | $0.20 | $1.00 |
| Cache write / 1M | $5.00 | $12.50 |
| Context window | 1M | 1M |
| Notes | New leading Opus model (Sep 22, 2026); Fable 5.1-level performance at 20% less than Opus 5; included on Pro/Max/Team at no extra cost | New top flagship (Sep 3, 2026); rolling out to Plus/Pro/Business/Enterprise; >272K tokens: $20/$75, cache $2 |
Claude Opus 5.5 is 2.5× cheaper on input tokens ($4.00 vs $10.00 per 1M). Claude Opus 5.5 is 2.5× cheaper on output tokens ($20.00 vs $50.00 per 1M).
| Workload | Claude Opus 5.5 | GPT-6 Astra | Difference |
|---|---|---|---|
| Support chatbot 10,000 conversations × (2,000 input + 400 output tokens) | $160 | $400 | Claude Opus 5.5 saves $240 |
| Document Q&A 1,000 questions × (30,000 input + 800 output tokens) | $136 | $340 | Claude Opus 5.5 saves $204 |
| Coding agent session 4M input tokens (90% cache hits) + 150,000 output tokens | $5.32 | $15.10 | Claude Opus 5.5 saves $9.78 |
Standard rates per 1M tokens from data on this site. The coding-agent row assumes 90% of input is read from the prompt cache (full input price where a model has no cache rate). Cache-write fees, batch discounts and long-context surcharges listed in the notes are not included. Updated November 2, 2026.
you run long-context or agentic workloads where prompts regularly exceed 272K tokens, or where most input is re-read from a prompt cache — Opus 5.5 keeps its standard rate across the full window and charges $0.20 per cached 1M tokens.
your product is already built on OpenAI's API and your prompts stay under 272K tokens, or your own evals show Astra completing tasks in fewer tokens or retries, which can offset its higher per-token price.
GPT-6 Astra's rate card has two bands: requests over 272K tokens are billed at 2× the input price, 1.5× the output price and 2× the cache-hit price. Anthropic's pricing page says Opus 5.5 includes the full 1M-token window at standard pricing — a 900K-token request is billed at the same per-token rate as a 9K one. If you feed whole repositories, long contracts or multi-hour transcripts into a single call, compare against Astra's long-context band, not its headline $10.00.
A cache hit on Opus 5.5 costs 5% of its input price ($0.20); on Astra it is $1.00, 10% of input. Writes cost $5.00 (5-minute cache) on Anthropic and $12.50 (30-minute cache) on OpenAI; Anthropic also sells a 1-hour cache at 2× input, OpenAI a 12-hour cache at a higher write rate. For an agent that re-sends a large system prompt and tool definitions every turn, the TTL matters as much as the rate: a short TTL that keeps expiring means paying the write fee again.
Both providers halve input and output prices for asynchronous Batch jobs, so the ratio between them holds for overnight evaluation or bulk-classification runs. OpenAI also offers a Flex tier at half price. Pinning traffic to a region costs extra on both: Anthropic applies 1.1× for US-only inference, OpenAI a 10% uplift on regional processing for eligible models.
Yes, on every standard rate: $4.00 vs $10.00 per 1M input tokens and $20.00 vs $50.00 per 1M output tokens. Cache hits are $0.20 vs $1.00.
Yes. Requests over 272K tokens are billed at a higher rate on input, output and cache hits. Claude Opus 5.5 has no long-context surcharge across its 1M window.
Yes. Anthropic's Batch API and OpenAI's Batch tier both cut input and output prices by 50% for non-urgent jobs; OpenAI's Flex tier is also half price.
Within Anthropic's lineup, Claude Sonnet 5.5 costs $2.00/$10.00 per 1M tokens. Whether it is good enough depends on your tasks — test it on your own prompts before switching.
How we choose: prices come from each vendor's official pricing page and are re-checked every week. We take no affiliate fees, so rankings aren't for sale.