GPT-5.6 Luna API cost calculator
GPT-5.6 Luna (OpenAI) is priced at $0.2 per million input tokens, $0.02 for cached input, and $1.20 per million output tokens — half that through the Batch API. Verified 2026-09-17 against OpenAI's pricing page.
What GPT-5.6 Luna costs for common workloads
| Workload | Per request | Per day | Per month |
|---|---|---|---|
| Support chatbotShort turns with a reused system prompt — 3k in, 400 out, 60% cached. | $0.0008 | $3.78 | $113 |
| RAG over documentsRetrieved context dominates — 12k in, 500 out, 30% cached. | $0.0024 | $3.53 | $106 |
| Coding agentGrowing context every turn — 20k in, 1.5k out, 80% cached. | $0.0029 | $8.76 | $263 |
| Batch classificationTiny prompts at volume through the Batch API — 800 in, 20 out. | $0.0001 | $18.40 | $552 |
Its blast radius when an agent loops
The coding-agent workload above at 30 requests a minute — $5.26 an hour — priced at each point a team usually finds out:
Hourly alert
$5.26
Next morning
$126
After a weekend
$315
Monthly invoice
$3,784