Prices → Compare → GPT-5.6 Luna vs Gemini 2.5 Flash-Lite
GPT-5.6 Luna vs Gemini 2.5 Flash-Lite: API cost compared
GPT-5.6 Luna lists at $0.100 in / $0.600 out per 1M tokens. Gemini 2.5 Flash-Lite lists at $0.100 in / $0.400. Sticker price only tells you so much — below is what each actually costs across eight production workloads.
Side by side
| GPT-5.6 Luna | Gemini 2.5 Flash-Lite | |
|---|---|---|
| Provider | OpenAI | |
| Input per 1M | $0.100 | $0.100 |
| Output per 1M | $0.600 | $0.400 |
| Cached input per 1M | $0.010 | not published |
| Context window | 400k | 1M |
| Blended per 1M (3:1) | $0.225 | $0.175 |
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 | Gemini 2.5 Flash-Lite | Cheaper | Difference |
|---|---|---|---|---|
| Customer support chatbot | $14.64 | $16.00 | GPT-5.6 Luna | $1.360 (9%) |
| RAG document Q&A | $19.60 | $20.80 | GPT-5.6 Luna | $1.200 (6%) |
| Coding agent | $10.45 | $14.80 | GPT-5.6 Luna | $4.350 (29%) |
| Bulk summarization | $138.60 | $136.00 | Gemini 2.5 Flash-Lite | $2.600 (2%) |
| Structured data extraction | $187.00 | $225.00 | GPT-5.6 Luna | $38.00 (17%) |
| Long-form content generation | $25.46 | $18.00 | Gemini 2.5 Flash-Lite | $7.460 (29%) |
| Email triage agent | $43.25 | $62.00 | GPT-5.6 Luna | $18.75 (30%) |
| Translation pipeline | $164.47 | $118.50 | Gemini 2.5 Flash-Lite | $45.97 (28%) |
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 4.0 for Gemini 2.5 Flash-Lite. 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.
Run your own numbers
Cost calculator
Enter your own numbers, or start from a workload preset. Costs are monthly and update as you type.
| Model | In /1M | Out /1M | Monthly | vs best |
|---|