Head to head · October 2026

GPT-6 Luna vs GPT-5.5 API pricing

GPT-6 Luna costs 57.3 times less per token at an 80/20 mix. Input costs 53.3x more on GPT-5.5. Output costs 60.4x more on GPT-5.5.

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

OpenAI

GPT-5.5

Reasoning-heavy tasks, research agents.

Vendor: OpenAI
Type: Frontier
SayGM in / out: $3.73 / $22.35
OpenRouter in / out: $5.28 / $31.65
Blended, 80/20: $7.454
Per 100M tokens: $745
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

GPT-6 Luna on SayGM
GPT-5.5 on SayGM

Side project5M in · 1M out

$0.72

$41

Production app50M in · 15M out

$9.05

$522

High volume500M in · 100M out

$72

$4,100

Show data as a table

	GPT-6 Luna on SayGM	GPT-5.5 on SayGM
Side project (5M in · 1M out)	$0.72	$41
Production app (50M in · 15M out)	$9.05	$522
High volume (500M in · 100M out)	$72	$4,100

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 GPT-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
GPT-6 LunaOpenAI	$0.07 / $0.37	$0.11 / $0.53	33% lower
GPT-5.5OpenAI	$3.73 / $22.35	$5.28 / $31.65	29% lower

Current SayGM rates

§ 04

GPT-6 Luna vs GPT-5.5 questions

Which is cheaper, GPT-6 Luna or GPT-5.5?

GPT-6 Luna is about 57.3 times cheaper than GPT-5.5 at an 80/20 input to output mix on SayGM, as of October 2026.

How much do GPT-6 Luna and GPT-5.5 cost on OpenRouter?

Including the 5.5 percent top-up fee, GPT-6 Luna costs $0.11 input and $0.53 output per million tokens, and GPT-5.5 costs $5.28 and $32.

Can I use GPT-6 Luna and GPT-5.5 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 GPT-5.5, or both can run in a cascade model.

§ 05