Head to head · October 2026

Claude Opus 5.5 vs GPT-5.6 Terra API pricing

GPT-5.6 Terra costs 2.1 times less per token at an 80/20 mix. Input costs 2.4x more on Claude Opus 5.5. Output costs 2.0x 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 Terra

General assistants, balanced cost and quality.

Vendor: OpenAI
Type: Frontier
SayGM in / out: $1.49 / $8.94
OpenRouter in / out: $2.11 / $12.66
Blended, 80/20: $2.980
Per 100M tokens: $298
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 Terra on SayGM

Side project5M in · 1M out

$36

$16

Production app50M in · 15M out

$445

$209

High volume500M in · 100M out

$3,558

$1,639

Show data as a table

	Claude Opus 5.5 on SayGM	GPT-5.6 Terra on SayGM
Side project (5M in · 1M out)	$36	$16
Production app (50M in · 15M out)	$445	$209
High volume (500M in · 100M out)	$3,558	$1,639

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 Terra 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 TerraOpenAI	$1.49 / $8.94	$2.11 / $12.66	29% lower

Current SayGM rates

§ 04

Claude Opus 5.5 vs GPT-5.6 Terra questions

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

GPT-5.6 Terra is about 2.1 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 Terra 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 Terra costs $2.11 and $13.

Can I use Claude Opus 5.5 and GPT-5.6 Terra 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 Terra and hard ones to Claude Opus 5.5, or both can run in a cascade model.

§ 05