Head to head · October 2026

Claude Fable 5.1 vs GPT-6 Luna API pricing

GPT-6 Luna costs 123.1 times less per token at an 80/20 mix. Input costs 127.0x more on Claude Fable 5.1. Output costs 120.1x more on Claude Fable 5.1.

Anthropic

Claude Fable 5.1

The hardest reasoning and agent tasks, where cost matters least.

Vendor: Anthropic
Type: Frontier
SayGM in / out: $8.89 / $44.45
OpenRouter in / out: $10.55 / $52.75
Blended, 80/20: $16.002
Per 100M tokens: $1,600
Output share of bill: 56%
SayGM vs OpenRouter: 16% lower

OpenAI

GPT-6 Luna

Chat products, summarisation, cheap tool calls.

Vendor: OpenAI
Type: Frontier
SayGM in / out: $0.07 / $0.37
OpenRouter in / out: $0.11 / $0.53
Blended, 80/20: $0.130
Per 100M tokens: $13
Output share of bill: 57%
SayGM vs OpenRouter: 33% lower

§ 01

Monthly bill at three usage levels

Both models on SayGM. The bars show how the price ratio turns into dollars as volume grows.

Fig. 1Monthly bill at three usage levels

Claude Fable 5.1 on SayGM
GPT-6 Luna on SayGM

Side project5M in · 1M out

$89

$0.72

Production app50M in · 15M out

$1,111

$9.05

High volume500M in · 100M out

$8,890

$72

Show data as a table

	Claude Fable 5.1 on SayGM	GPT-6 Luna on SayGM
Side project (5M in · 1M out)	$89	$0.72
Production app (50M in · 15M out)	$1,111	$9.05
High volume (500M in · 100M out)	$8,890	$72

Usage is millions of input and output tokens per month. No caching discount applied. Source: published rate cards, October 2026 snapshot. Current prices on saygm.com.

§ 02

Verdict

A common pattern is to send routine requests to GPT-6 Luna and escalate to Claude Fable 5.1 on failure or low confidence. On one key, that is a model name change per request rather than a second provider account.

§ 03

Per-token prices

OpenRouter figures include its 5.5% top-up fee.

USD per million tokens, input and output. OpenRouter includes its 5.5% top-up fee. Snapshot from October 2026.
Model	SayGMin / out	OpenRouterin / out, fee incl.	SayGM vs OpenRouter80/20 blend
Claude Fable 5.1Anthropic	$8.89 / $44.45	$10.55 / $52.75	16% lower
GPT-6 LunaOpenAI	$0.07 / $0.37	$0.11 / $0.53	33% lower

Current SayGM rates

§ 04

Claude Fable 5.1 vs GPT-6 Luna questions

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

GPT-6 Luna is about 123.1 times cheaper than Claude Fable 5.1 at an 80/20 input to output mix on SayGM, as of October 2026.

How much do Claude Fable 5.1 and GPT-6 Luna cost on OpenRouter?

Including the 5.5 percent top-up fee, Claude Fable 5.1 costs $11 input and $53 output per million tokens, and GPT-6 Luna costs $0.11 and $0.53.

Can I use Claude Fable 5.1 and GPT-6 Luna with one API key?

Yes. SayGM serves both through their native APIs on a single key, so simple tasks can go to GPT-6 Luna and hard ones to Claude Fable 5.1, or both can run in a cascade model.

§ 05