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Claude Fable 5.1 vs GPT-6 Astra API Cost

Claude Fable 5.1 and GPT-6 Astra both list at $10 in and $50 out. Fable 5.1's cache hits cost a quarter as much. See what that is worth to you.

Updated · By Niraj Kumar · 6 sources

Models

Each request

Count text inCount text in
tokens

System prompt, conversation history, documents and tool definitions are all resent on every call.

tokens

The visible answer.

Count tokens from a prompt or JSON payloadShow

Plain text, OpenAI Chat or Responses JSON, or Anthropic Messages JSON. A final assistant message or a response body counts as output. Counted in your browser; nothing is uploaded.

Loading the tokenizer…

Counts use OpenAI's o200k tokenizer, so they are exact for GPT-6 and GPT-5 models, plus a few tokens of message framing. Other providers' tokenizers count the same text differently and do not publish a conversion factor; Anthropic says Claude models from 4.7 on produce about 30% more tokens than earlier Claude models. For an exact count on another model, paste one of its API responses: the usage it reports is shown above.

tokens

Thinking tokens are billed as output. Leave at 0 for models or settings that do not reason.

Volume

PricePrice

30,000 requests over 30 days.

Discounts

%
0%100%

The share of input that repeats exactly at the start of every request, such as a fixed system prompt. The prompt caching calculator prices cache writes and expiry in detail.

Batch APIBatch API
Monthly cost$1,650Both sides are the same price.
Claude Fable 5.1
$1,650 a month
$0.055 a request · 23rd cheapest of 24
GPT-6 Astra
$1,650 a month
$0.055 a request · 24th cheapest of 24
Cheapest listed model
Claude Haiku 5.5
$16.50 a month
Side by side
MeasureClaude Fable 5.1GPT-6 Astra
Input, per 1M tokens$10$10
Cache hit, per 1M tokens$0.25$1
Output, per 1M tokens$50$50
Context window1M tokens1.05M tokens
Max output128K tokens128K tokens
Batch discount50%50%
Long-context surchargeNoneAbove 272K input
Input cost a month$900.00$900.00
Output cost a month$750.00$750.00
Every model on this workload, per month3,000 tokens in, 500 out, 1,000 a day. Hover or focus a row for rates.
  1. 1Claude Haiku 5.5Anthropic$16.50
  2. 2GPT-6 LunaOpenAI$16.50
  3. 3Qwen3.8 FlashAlibaba$20.55
  4. 4GPT-5.6 LunaOpenAI$36.00
  5. 5DeepSeek V4.1 FlashDeepSeek$45.00
  6. 6Qwen3.7 PlusAlibaba$60.00
  7. 7Gemini 3.5 Flash-LiteGoogle$64.50
  8. 8Gemini 3.8 FlashGoogle$123.75
  9. 9Grok 4.3xAI$150.00
  10. 10Claude Haiku 4.5Anthropic$165.00
  11. 11DeepSeek V4 ProDeepSeek$178.20
  12. 12Grok 4.7xAI$270.00
  13. 13Qwen3.8 MaxAlibaba$270.00
  14. 14Claude Sonnet 5.5Anthropic$330.00
  15. 15Claude Sonnet 5Anthropic$330.00
  16. 16GPT-6.1 SolOpenAI$330.00
  17. 17GPT-6 SolOpenAI$330.00
  18. 18GPT-5.6 TerraOpenAI$360.00
  19. 19Gemini 3.1 ProGoogle$360.00
  20. 20Claude Opus 5.5Anthropic$660.00
  21. 21GPT-5.6 SolOpenAI$660.00
  22. 22Claude Opus 5Anthropic$825.00
  23. 23Claude Fable 5.1Anthropic$1,650
  24. 24GPT-6 AstraOpenAI$1,650

How the Claude Fable 5.1 vs GPT-6 Astra API Cost works

cost = (fresh input × input rate + cached input × cache rate + (output + reasoning) × output rate) ÷ 1,000,000

This page uses the same method as the LLM API Cost Calculator, which explains each term and assumption in full.

Worked example

A chat feature sending 3,000 input tokens and getting 500 back, 1,000 times a day, priced on both models with no caching.

  1. 1Claude Fable 5.1: 3,000 × $10 + 500 × $50, ÷ 1,000,000 = $0.055 a request, $1,650 a month
  2. 2GPT-6 Astra: 3,000 × $10 + 500 × $50, ÷ 1,000,000 = $0.055 a request, $1,650 a month
  3. 3Difference: none at list rates

Both cost $1,650 a month at list rates; caching, long prompts and token counts decide which is cheaper in practice.

Frequently asked questions

Which is cheaper, Claude Fable 5.1 or GPT-6 Astra?

At standard list rates, they cost the same on a typical chat request (3,000 tokens in, 500 out); they cost the same on output-heavy generation (500 in, 2,000 out); and Claude Fable 5.1 is 21% cheaper than GPT-6 Astra on a large cached prompt (20,000 in, 90% cached, 500 out). Claude Fable 5.1 charges $10 input and $50 output per million tokens; GPT-6 Astra charges $10 and $50.

Why can Claude Fable 5.1 come out cheaper than GPT-6 Astra at the same list price?

Caching and long prompts. Fable 5.1 charges $0.25 per million tokens for a cache hit, a quarter of Astra's $1, so any workload with a large repeated prefix costs less on Fable. Astra also bills the whole request at $20 and $75 once a prompt passes 272,000 tokens, where Fable 5.1 keeps $10 and $50 across its 1M-token window.

Sources

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