Head to head · October 2026

Claude Opus 5.5 vs GPT-5.6 Luna API pricing

GPT-5.6 Luna costs 21.5 times less per token at an 80/20 mix. Input costs 23.7x more on Claude Opus 5.5. Output costs 20.0x more on Claude Opus 5.5.

Anthropic

Claude Opus 5.5

Agentic coding, long multi-step tasks, hard reasoning.

Vendor: Anthropic
Type: Frontier
SayGM in / out: $3.56 / $17.78
OpenRouter in / out: $4.22 / $21.10
Blended, 80/20: $6.404
Per 100M tokens: $640
Output share of bill: 56%
SayGM vs OpenRouter: 16% lower

OpenAI

GPT-5.6 Luna

Chat products, summarisation, cheap tool calls.

Vendor: OpenAI
Type: Frontier
SayGM in / out: $0.15 / $0.89
OpenRouter in / out: $0.21 / $1.27
Blended, 80/20: $0.298
Per 100M tokens: $30
Output share of bill: 60%
SayGM vs OpenRouter: 29% 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 Opus 5.5 on SayGM
GPT-5.6 Luna on SayGM

Side project5M in · 1M out

$36

$1.64

Production app50M in · 15M out

$445

$21

High volume500M in · 100M out

$3,558

$164

Show data as a table

	Claude Opus 5.5 on SayGM	GPT-5.6 Luna on SayGM
Side project (5M in · 1M out)	$36	$1.64
Production app (50M in · 15M out)	$445	$21
High volume (500M in · 100M out)	$3,558	$164

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-5.6 Luna and escalate to Claude Opus 5.5 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 Opus 5.5Anthropic	$3.56 / $17.78	$4.22 / $21.10	16% lower
GPT-5.6 LunaOpenAI	$0.15 / $0.89	$0.21 / $1.27	29% lower

Current SayGM rates

§ 04

Claude Opus 5.5 vs GPT-5.6 Luna questions

Which is cheaper, Claude Opus 5.5 or GPT-5.6 Luna?

GPT-5.6 Luna is about 21.5 times cheaper than Claude Opus 5.5 at an 80/20 input to output mix on SayGM, as of October 2026.

How much do Claude Opus 5.5 and GPT-5.6 Luna cost on OpenRouter?

Including the 5.5 percent top-up fee, Claude Opus 5.5 costs $4.22 input and $21 output per million tokens, and GPT-5.6 Luna costs $0.21 and $1.27.

Can I use Claude Opus 5.5 and GPT-5.6 Luna with one API key?

Yes. SayGM serves both through their native APIs on a single key, so simple tasks can go to GPT-5.6 Luna and hard ones to Claude Opus 5.5, or both can run in a cascade model.

§ 05