GPT-5.5 Pro vs Claude Fable 5: cost compared
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Claude Fable 5 is 67% cheaper on input and 72% cheaper on output than GPT-5.5 Pro. Whether that makes it the right choice depends entirely on whether it does your task well enough — this page gives you the cost side of that trade, precisely.
Rates side by side
| $ per million tokens | GPT-5.5 Pro | Claude Fable 5 |
|---|---|---|
| Input | $30.00 | $10.00 |
| Output | $180.00 | $50.00 |
| Cached input | — | $1.00 |
| Batch input | — | $5.00 |
| Output : input ratio | 6.0× | 5.0× |
What the difference is worth
Monthly cost for the same workload on each, without caching:
| Workload | GPT-5.5 Pro | Claude Fable 5 | Difference |
|---|---|---|---|
| Support chatbot 1,000 conversations/month · 2,000 in + 500 out each | $150 | $45.00 | $105 saved |
| RAG search 10,000 queries/month · 8,000 in + 400 out each | $3120 | $1000 | $2120 saved |
| Bulk extraction 10,000 documents · 3,000 in + 300 out each | $1440 | $450 | $990 saved |
| Coding agent 100 runs/month · 400,000 in + 20,000 out each | $1560 | $500 | $1060 saved |
Which to use
Claude Fable 5 if the task is well-specified and mechanical — extraction, classification, formatting, routine transformation. The saving is real and compounds with volume.
GPT-5.5 Pro if the task involves genuine reasoning, long-horizon planning, or work where a wrong answer is expensive to catch. Paying 3.0× more on input is trivial compared to the cost of shipping a bad result.
These are different providers, so switching means a different SDK and a different tokenizer. The same text is a different number of tokens on each, so the price difference above is approximate at the margin. Measure token counts on your real inputs before committing.
Don't skip caching
Where prompt caching is available, it frequently matters more than the choice between these two.
Sources
OpenAI rates verified 2026-08-05 (source). Anthropic rates verified 2026-08-05 (source).