Prices → Compare → GPT-5.6 Luna vs Claude Sonnet 5
GPT-5.6 Luna vs Claude Sonnet 5: API cost compared
GPT-5.6 Luna lists at $0.100 in / $0.600 out per 1M tokens. Claude Sonnet 5 lists at $2.000 in / $10.00. Sticker price only tells you so much — below is what each actually costs across eight production workloads.
Side by side
| GPT-5.6 Luna | Claude Sonnet 5 | |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Input per 1M | $0.100 | $2.000 |
| Output per 1M | $0.600 | $10.00 |
| Cached input per 1M | $0.010 | $0.200 |
| Context window | 400k | 200k |
| Blended per 1M (3:1) | $0.225 | $4.000 |
Monthly cost by workload
Caching applied at each workload's typical hit rate. This is where the two models actually separate.
| Workload | GPT-5.6 Luna | Claude Sonnet 5 | Cheaper | Difference |
|---|---|---|---|---|
| Customer support chatbot | $14.64 | $257.80 | GPT-5.6 Luna | $243.16 (94%) |
| RAG document Q&A | $19.60 | $368.00 | GPT-5.6 Luna | $348.40 (95%) |
| Coding agent | $10.45 | $185.00 | GPT-5.6 Luna | $174.55 (94%) |
| Bulk summarization | $138.60 | $2,692 | GPT-5.6 Luna | $2,553 (95%) |
| Structured data extraction | $187.00 | $3,490 | GPT-5.6 Luna | $3,303 (95%) |
| Long-form content generation | $25.46 | $429.20 | GPT-5.6 Luna | $403.74 (94%) |
| Email triage agent | $43.25 | $805.00 | GPT-5.6 Luna | $761.75 (95%) |
| Translation pipeline | $164.47 | $2,810 | GPT-5.6 Luna | $2,645 (94%) |
How to read this
GPT-5.6 Luna is cheaper on the majority of these workloads, but "majority" is not the decision. The output:input price ratio is 6.0 for GPT-5.6 Luna and 5.0 for Claude Sonnet 5. If your traffic is output-heavy — long-form drafting, translation — the model with the lower output price wins regardless of what the input price suggests. If you are input-heavy — RAG, bulk summarization, agents re-reading a codebase — the cached input rate matters more than either headline number.
Cost is also not the only axis. This site does not benchmark quality, latency, or rate limits, and a model that is 3x cheaper but needs two attempts per task is not cheaper. Use these numbers to size a bill, then validate on your own evals.
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Cost calculator
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| Model | In /1M | Out /1M | Monthly | vs best |
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