Cheaper alternatives to Claude Opus 5.5
Claude Opus 5.5 costs $4 / $20 per 1M input / output tokens and scores 168 on Epoch AI’s Capabilities Index. 4 current models score within its margin of error for less, the cheapest being GPT-6.1 Terra at 75% less. Prices checked 13 Oct – 6 Nov 2026.
Similar capability, lower price
Highest score first
| Model | Capability | Input / output per 1M | Cheaper by | Customer chat assistant, a month | Compare |
|---|---|---|---|---|---|
 GPT-6.1 TerraOpenAI |
168level, within the margin | $1.00 / $5.00 | 75% | $153 | Compare |
| GPT-6.1 SolOpenAI |
168level, within the margin | $2.00 / $10.00 | 50% | $305 | Compare |
 Claude Sonnet 5.5Anthropic |
167level, within the margin | $2.00 / $10.00 | 50% | $305 | Compare |
 Gemini 4 ArgonGoogle |
166level, within the margin | $2.00 / $10.00 | 50% | $305 | Compare |
A step down, for much less
Highest score first
| Model | Capability | Input / output per 1M | Cheaper by | Customer chat assistant, a month | Compare |
|---|---|---|---|---|---|
| Claude Haiku 5.5Anthropic |
1608 below | $0.10 / $0.50 | 98% | $15.50 | Compare |
| Gemini 3.8 FlashGoogle |
15810 below | $0.75 / $3.75 | 81% | $116 | Compare |
 Qwen3.8 MaxAlibaba |
15810 below | $2.00 / $6.00 | 63% | $320 | Compare |
 Kimi K3Moonshot AI · open weights |
15810 below | $3.00 / $15.00 | 25% | $465 | Compare |
| GPT-6 LunaOpenAI |
15711 below | $0.10 / $0.50 | 98% | $15.50 | Compare |
 Muse Spark 1.3Meta |
15711 below | $1.25 / $4.25 | 75% | $155 | Compare |
 DeepSeek V4.1 FlashDeepSeek |
15612 below | $0.30 / $1.20 | 93% | $39.30 | Compare |
 GLM-5.3Z.ai |
15612 below | $1.40 / $4.40 | 73% | $171 | Compare |
Other frontier models, not yet scored
| Model | Capability | Input / output per 1M | Cheaper by | Customer chat assistant, a month | Compare |
|---|---|---|---|---|---|
| Kimi K3.1 ProMoonshot AI |
Not scored | $2.00 / $10.00 | 50% | $310 | Compare |
What switching saves on three workloads
Per month, list prices
| Workload | Claude Opus 5.5 | GPT-6.1 Terra | Claude Sonnet 5.5 | Claude Haiku 5.5 |
|---|---|---|---|---|
| Customer chat assistant100M in, 20M out, 50% cached | $610 | $153 | $305 | $15.50 |
| Document Q&A (RAG)240M in, 12M out, 30% cached | $926 | $232 | $463 | $23.52 |
| Coding agent750M in, 8M out, 85% cached | $738 | $184 | $369 | $21.63 |
Monthly cost at list prices with no batch discount. Your own numbers: open these models in the cost calculator.
How to choose
- Same quality, smaller bill: GPT-6.1 Terra scores level with Claude Opus 5.5 and costs 75% less. Test it on your hardest prompts first.
- Stay with Anthropic: Claude Sonnet 5.5 keeps the same API, tools and data terms at $2 / $10.
- Mix models: send routine requests to a cheaper model and keep Claude Opus 5.5 for the hard ones. How much that saves depends on your traffic, so measure quality on a sample before switching everything.
- Cut the bill without switching: batch processing and prompt caching often save more than changing model. See how to cut your API bill in half.
Questions
What is the cheapest alternative to Claude Opus 5.5 with similar capability?
GPT-6.1 Terra from OpenAI, at $1 / $5 per 1M input / output tokens, 75% less than Claude Opus 5.5 at a typical 3:1 mix. On Epoch AI’s Capabilities Index it scores 168 against 168, within the margin of error.
Is GPT-6.1 Terra as good as Claude Opus 5.5?
On general benchmarks, they’re level: Epoch AI’s Capabilities Index gives GPT-6.1 Terra 168 (range 165–173) and Claude Opus 5.5 168 (165–173). Benchmarks don’t cover every task, so run both on a sample of your own work before switching.
How much would I save by switching from Claude Opus 5.5?
For a customer chat assistant (100M input and 20M output tokens a month, half the input cached), Claude Opus 5.5 costs $610 a month. GPT-6.1 Terra costs $153, Claude Sonnet 5.5 $305.
Is there a cheaper Anthropic model than Claude Opus 5.5?
Yes: Claude Sonnet 5.5 ($2 / $10, capability 167), Claude Haiku 5.5 ($0.10 / $0.50, capability 160). Staying with Anthropic keeps your prompts, tools and billing the same.
Why isn’t every cheaper model listed?
We list current models that cost less than Claude Opus 5.5 at a 3:1 input-to-output mix and either score within about 12 points of it on Epoch AI’s index or are in the same tier without a score yet. Much weaker models are cheaper still but rarely a like-for-like swap.
Capability: Epoch Capabilities Index by Epoch AI, CC BY 4.0, read 4 Nov 2026. Prices from each provider’s own page, linked on every model page.