Head to head · October 2026

Claude Fable 5.1 vs Claude Sonnet 5 API pricing

Claude Sonnet 5 costs 5.0 times less per token at an 80/20 mix. Input costs 5.0x more on Claude Fable 5.1. Output costs 5.0x 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

Anthropic

Claude Sonnet 5

Daily coding in Cursor, Cline and Claude Code.

Vendor: Anthropic
Type: Frontier
SayGM in / out: $1.78 / $8.89
OpenRouter in / out: $2.11 / $10.55
Blended, 80/20: $3.202
Per 100M tokens: $320
Output share of bill: 56%
SayGM vs OpenRouter: 16% 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
Claude Sonnet 5 on SayGM

Side project5M in · 1M out

$89

$18

Production app50M in · 15M out

$1,111

$222

High volume500M in · 100M out

$8,890

$1,779

Show data as a table

	Claude Fable 5.1 on SayGM	Claude Sonnet 5 on SayGM
Side project (5M in · 1M out)	$89	$18
Production app (50M in · 15M out)	$1,111	$222
High volume (500M in · 100M out)	$8,890	$1,779

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 Claude Sonnet 5 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
Claude Sonnet 5Anthropic	$1.78 / $8.89	$2.11 / $10.55	16% lower

Current SayGM rates

§ 04

Claude Fable 5.1 vs Claude Sonnet 5 questions

Which is cheaper, Claude Fable 5.1 or Claude Sonnet 5?

Claude Sonnet 5 is about 5.0 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 Claude Sonnet 5 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 Claude Sonnet 5 costs $2.11 and $11.

Can I use Claude Fable 5.1 and Claude Sonnet 5 with one API key?

Yes. SayGM serves both through their native APIs on a single key, so simple tasks can go to Claude Sonnet 5 and hard ones to Claude Fable 5.1, or both can run in a cascade model.

§ 05