★ Head-to-head

Claude Fable 5.1 vs GPT-6 Astra: API Cost Comparison

Top-tier models from both labs, with the same list price per million tokens. The difference is in caching and long-prompt surcharges.

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Updated 7 Nov 2026

Claude Fable 5.1 and GPT-6 Astra pricing side by side
Side by side	Claude Fable 5.1 Anthropic	GPT-6 Astra OpenAI
Input / 1M	$10	$10
Output / 1M	$50	$50
Cached input / 1M	$0.25	$1
Batch discount	50% off	50% off
Context window	Not published	1.05M tokens
Long-prompt surcharge	None	Above 272K input
Tier	Frontier	Frontier

Workload

Requests per day

Avg input tokens

tok

Avg output tokens

tok

Cached input

Repeated system prompt or docs

Batched requests

Jobs that can wait hours

Models

Anthropic

OpenAI

Google

Mistral

DeepSeek

$ per 1M tokens, input / output

Monthly cost · 30 days

Cheapest: $10,500; Claude Fable 5.1
Priciest: $10,500; GPT-6 Astra
Spread: 1.0×; priciest vs cheapest

	Per request		Per 1K users / mo
Claude Fable 5.1	$0.0350	$10,500	$5,250
GPT-6 Astra	$0.0350	$10,500	$5,250

Per 1K users assumesrequests per user per day.

Where the money is

Caching half your input on GPT-6 Astra (a shared system prompt or document) would cut about $2,700/month.

You're looking at ~$10,500/month.

Most AI products I audit can cut that 30–60% with routing, caching and shorter prompts.

Get a cost-cutting audit

Cost at three traffic levels

Same request on both: 2,000 input tokens and 300 output tokens, no caching, no batch, 30-day month.

Monthly cost of Claude Fable 5.1 vs GPT-6 Astra
Requests / day	Claude Fable 5.1	GPT-6 Astra	Difference
1,000	$1,050	$1,050	$0
10,000	$10,500	$10,500	$0
100,000	$105,000	$105,000	$0

By request type:

Cost per 1,000 calls by request type, Claude Fable 5.1 vs GPT-6 Astra
Per 1K calls	Claude Fable 5.1	GPT-6 Astra
Classification or routing call	$4.50	$4.50
Support chat reply	$27.50	$27.50
RAG answer over your docs	$80.00	$80.00
Long document summary	$450	$450

When to pick which

Input tokens cost the same on both ($10 per 1M).
Output tokens cost the same on both ($50 per 1M).
Cache reads are 4.0× cheaper on Claude Fable 5.1 ($0.25 vs $1 per 1M), so it pulls ahead when your prompts share a long fixed prefix.
Both offer 50% off for batch processing.
GPT-6 Astra bills the whole request at a higher rate once input passes 272,000 tokens.

Claude Fable 5.1: Anthropic's top tier. Long-horizon agentic work and the hardest reasoning, where a wrong answer costs more than the tokens.

GPT-6 Astra: OpenAI's flagship for complex reasoning and coding, when quality matters more than cost.

Verdict

It's a wash on price

On list price they are a wash for a typical request. Decide on quality for your task, latency, and which caching model fits your prompts. Then run both on 50 of your real prompts and compare answers and billed tokens side by side.

How the math works

Every provider bills input tokens (your prompt, system prompt and retrieved documents) and output tokens (the reply) separately, per million. Output is usually 4–5× the input price, so chatty apps are output-heavy and RAG apps are input-heavy.

cost per request = (fresh_in × input_price

+ cached_in × cached_price

+ out × output_price) / 1,000,000

× (1 − batched_share × batch_discount)

monthly = cost per request × requests per day × 30

Two adjustments are applied automatically. Introductory prices (currently on some Gemini models) are used until their end date. Long-prompt surcharges kick in when your average input crosses the provider's threshold: 272K tokens on current OpenAI models, 100K on Claude Haiku 5.5.

Not modelled: cache-write premiums, priority or fast tiers, regional surcharges, image and audio tokens, and reasoning tokens a model spends before answering (they bill as output, so add them to your output estimate if you use extended thinking).

Questions

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

For a typical request of 2,000 input and 300 output tokens they cost about the same: $0.0350 on Claude Fable 5.1 and $0.0350 on GPT-6 Astra. Caching and output length decide which is cheaper for your workload.

Can I use both Claude Fable 5.1 and GPT-6 Astra?

Yes, and many teams do. Put a thin routing layer in front of both: send the requests that need the stronger or larger-context model to it, and everything else to the cheaper one. Keep prompts provider-neutral so you can move traffic when prices change.

How often do Anthropic and OpenAI change prices?

Often enough that a comparison older than a few months is suspect. The prices on this page were verified on 7 Nov 2026 from each provider's own documentation, linked in the Sources section.

Sources

All prices are list prices from each provider's own documentation, standard tier, in USD, last verified on 7 Nov 2026. Providers change prices often; if a number here disagrees with the source, the source wins.

Claude Fable 5.1platform.claude.com
GPT-6 Astradevelopers.openai.com

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I'm Himanshu, an AI and full-stack engineer. I build MVPs, AI agents and the growth plumbing around them for early-stage startups.

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