Choose Anthropic: Claude Opus 4.8 if…
- cost matters at scale — it is 50% cheaper on a typical 3:1 input/output mix ($875 vs $1,750 a month for 50,000 support chats)
Anthropic: Claude Opus 4.8 vs OpenAI: GPT-6 Astra Pro
Neither wins outright: Anthropic: Claude Opus 4.8 is the pick when cost matters at scale, OpenAI: GPT-6 Astra Pro when you need seed (reproducible sampling).
Key numbers
| Spec | Anthropic: Claude Opus 4.8 | OpenAI: GPT-6 Astra Pro |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input price (per 1M tokens) | $5.00 | $10.00 |
| Output price (per 1M tokens) | $25.00 | $50.00 |
| Blended price (3:1 input/output) | $10.00 | $20.00 |
| Cheaper than … of all models we track | 5% | 3% |
| Context window | 1M tokens (~1,500 pages) | 1.1M tokens (~1,575 pages) |
| Larger context than … of all models | 69% | 93% |
| Max output per response | 128K tokens (~96,000 words) | 128K tokens (~96,000 words) |
| Input types | text, image, file | file, image, text |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2026-05-27 | 2026-09-04 |
Advertisement
What it costs for real workloads
Monthly cost at list price for five common workloads. Token counts per unit are stated so you can scale them to your own traffic. A workload that does not fit a model's context window is marked rather than priced.
| Workload (per month) | Anthropic: Claude Opus 4.8 | OpenAI: GPT-6 Astra Pro | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $875 | $1,750 | Anthropic: Claude Opus 4.8 saves $875 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $850 | $1,700 | Anthropic: Claude Opus 4.8 saves $850 |
| Coding / tool-using agent 2,000 tasks — each a multi-step task with tool calls and file context (60,000 in / 6,000 out tokens) | $900 | $1,800 | Anthropic: Claude Opus 4.8 saves $900 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $550 | $1,100 | Anthropic: Claude Opus 4.8 saves $550 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $275 | $550 | Anthropic: Claude Opus 4.8 saves $275 |
Capabilities side by side
| Capability | Anthropic: Claude Opus 4.8 | OpenAI: GPT-6 Astra Pro | What it lets you do |
|---|---|---|---|
| Tool / function calling | ✓ Yes | ✓ Yes | call your APIs and run agent loops |
| Structured output (JSON schema) | ✓ Yes | ✓ Yes | return JSON that validates against your schema |
| Reasoning / thinking mode | ✓ Yes | ✓ Yes | spend extra tokens thinking before answering hard problems |
| Image input | ✓ Yes | ✓ Yes | read screenshots, charts and scanned pages |
| Audio input | — | — | take speech or audio directly |
| File / PDF input | ✓ Yes | ✓ Yes | accept documents without your own parsing step |
| Image output | — | — | generate images, not just text |
| Built-in web search | ✓ Yes | ✓ Yes | answer from live web results |
| Seed (reproducible sampling) | — | ✓ Yes | repeat a generation for tests and evals |
| Log-probabilities | — | — | read token confidence for classification and scoring |
From each model's published parameters and input/output types. “—” means not advertised, not proven absent.
Price history
- Anthropic: Claude Opus 4.8: price unchanged since we started tracking it on 2026-08-06.
- OpenAI: GPT-6 Astra Pro: price unchanged since we started tracking it on 2026-09-05.
Which should you choose?
Choose OpenAI: GPT-6 Astra Pro if…
- you need seed (reproducible sampling) — to repeat a generation for tests and evals; Anthropic: Claude Opus 4.8 does not advertise it
- you want the newer model — released 2026-09-04, 3 months after the other
Frequently asked questions
Is Anthropic: Claude Opus 4.8 better than OpenAI: GPT-6 Astra Pro?
Neither wins outright: Anthropic: Claude Opus 4.8 is the pick when cost matters at scale, OpenAI: GPT-6 Astra Pro when you need seed (reproducible sampling). In short: Anthropic: Claude Opus 4.8 when cost matters at scale; OpenAI: GPT-6 Astra Pro when you need seed (reproducible sampling), you want the newer model.
Which is cheaper, Anthropic: Claude Opus 4.8 or OpenAI: GPT-6 Astra Pro?
Anthropic: Claude Opus 4.8 is cheaper: $10.00 vs $20.00 per 1M tokens at a typical 3:1 input/output mix, 50% less. For 50,000 support conversations a month that is $875 against $1,750.
How much do Anthropic: Claude Opus 4.8 and OpenAI: GPT-6 Astra Pro cost per million tokens?
Anthropic: Claude Opus 4.8 costs $5.00 per 1M input tokens and $25.00 per 1M output tokens; OpenAI: GPT-6 Astra Pro costs $10.00 input and $50.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, Anthropic: Claude Opus 4.8 or OpenAI: GPT-6 Astra Pro?
OpenAI: GPT-6 Astra Pro: 1.1M tokens, about 1,575 pages, against 1M (about 1,500 pages) for Anthropic: Claude Opus 4.8.
Do Anthropic: Claude Opus 4.8 and OpenAI: GPT-6 Astra Pro support function calling and JSON output?
Tool calling — Anthropic: Claude Opus 4.8: yes, OpenAI: GPT-6 Astra Pro: yes. JSON-schema structured output — Anthropic: Claude Opus 4.8: yes, OpenAI: GPT-6 Astra Pro: yes.
Can Anthropic: Claude Opus 4.8 or OpenAI: GPT-6 Astra Pro read images?
Yes, both accept image input.
Is Anthropic: Claude Opus 4.8 or OpenAI: GPT-6 Astra Pro free to use?
No free variant is listed for either; both are pay-per-token.
What is the maximum output length of Anthropic: Claude Opus 4.8 and OpenAI: GPT-6 Astra Pro?
Anthropic: Claude Opus 4.8 can write up to 128K tokens (about 96,000 words) per response; OpenAI: GPT-6 Astra Pro up to 128K (about 96,000 words).
When were Anthropic: Claude Opus 4.8 and OpenAI: GPT-6 Astra Pro released?
Anthropic: Claude Opus 4.8 was listed on 2026-05-27; OpenAI: GPT-6 Astra Pro on 2026-09-04.
About the two models
Anthropic: Claude Opus 4.8
Claude Opus 4.8 is Anthropic's most capable generally available model in the Opus family. It supports text, image, and file inputs with text output, with reasoning support and a 1M-token...
Full Anthropic: Claude Opus 4.8 specs →OpenAI: GPT-6 Astra Pro
GPT-6 Astra Pro is the same underlying model as [GPT-6 Astra](https://openrouter.ai/openai/gpt-6-astra), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. **Cost note:** pro mode spends far more...
Full OpenAI: GPT-6 Astra Pro specs →