GPT-5.6 Luna vs Gemini 2.5 Flash
Side-by-side comparison of API pricing, specs, benchmarks, and capabilities
| Specification |
by OpenAI
|
by Google
|
|---|---|---|
| Overview | ||
| Status | Current mid tier | Deprecated budget |
| Released | Jul 9, 2026 | Jun 17, 2025 |
| Pricing per million tokens | ||
| Input | $0.200/Mtok | $0.300/Mtok |
| Output | $1.20/Mtok | $2.50/Mtok |
| Blended avg | $0.450/Mtok | $0.850/Mtok |
| Cached input | $0.020/Mtok | — |
| Specifications | ||
| Context window | 1M tokens | 1M tokens |
| Parameters | Proprietary | Proprietary |
| Speed (TPS) | — | — |
| Modalities | ||
| Input |
textimage
|
textimageaudiovideo
|
| Benchmarks source: Vellum LLM Leaderboard | ||
| Avg benchmark score | 90.7 | 50.2 |
| Perf / dollar | 201.6 | 59.1 |
| GPQA Diamond | 92.3 | 78.3 |
| SWE-Bench Verified | 93 | 38 |
| Terminal-Bench 2.1 | 84.3 | 16.9 |
| LiveCodeBench | — | 63.5 |
| Humanity's Last Exam | — | 12.1 |
| ARC-AGI 2 | — | 15 |
| AIME 2025 | — | 78 |
| MMMLU | — | 78 |
| HumanEval | 93 | — |
| MATH 500 | — | 72 |
| Independent composite scores each on its own scale — not part of the average above | ||
| AA Intelligence Index | 52.3 | — |
| AA Agentic Index | 46.9 | — |
| AA-Omniscience Index (−100–100) | -10.3 | — |
| GDPval-AA v2 | 1569.1 ELO | — |
| LMSYS Chatbot Arena | — | 1409.8 ELO |
| Providers | ||
| Available from |
OpenAI — $0.200/$1.20/Mtok
|
Google — $0.300/$2.50/Mtok
|
Cost at scale
1M tokens · 50/50 input/output| Volume | GPT-5.6 Luna | Gemini 2.5 Flash | Savings |
|---|---|---|---|
| 1M tokens | $0.45 | $0.85 | $0.4 (47.1%) |
| 10M tokens | $4.5 | $8.5 | $4 (47.1%) |
| 100M tokens | $45 | $85 | $40 (47.1%) |
| 1000M tokens | $450 | $850 | $400 (47.1%) |
When to pick which
distilled from the pricing and spec data above- cost dominates: $0.450/Mtok blended vs $0.850 — 47.1% less on the same 50/50 token mix
- your workload re-reads context (agents, RAG, long chats): cached input costs $0.020/Mtok — 90% off its list input price, a discount Gemini 2.5 Flash doesn't offer
- raw capability matters more than price: 90.7 vs 50.2 average benchmark score
- this pairing gives Gemini 2.5 Flash no edge on price, context, cache discount, or measured performance — pick it only for qualitative fit (ecosystem, compliance, model behavior on your prompts)
Price movement
recorded changes since we began tracking each model · last checked Aug 28, 2026| Model | Changes | Latest move | Old → new $/M |
|---|---|---|---|
| GPT-5.6 Luna | 1 | price cut on Aug 1, 2026 | $1/$6 → $0.2/$1.2/Mtok |
| Gemini 2.5 Flash | 2 | price rise on Jul 4, 2026 | $0.075/$0.3 → $0.3/$2.5/Mtok |
The cheaper option here — GPT-5.6 Luna costs $0.450/Mtok blended on OpenAI.
Summary
GPT-5.6 Luna by OpenAI costs $0.200/Mtok input and $1.20/Mtok output, with a 1M-token context window. It supports text, image input.
Gemini 2.5 Flash by Google costs $0.300/Mtok input and $2.50/Mtok output, with a 1M-token context window. It supports text, image, audio, video input.
On a blended cost basis, GPT-5.6 Luna is 47.1% cheaper than Gemini 2.5 Flash.It also has a larger context window.
On benchmarks, GPT-5.6 Luna scores higher (90.7 vs 50.2) on average. In terms of value, GPT-5.6 Luna has better performance per dollar (201.6 vs 59.1).
Note: Pricing is per million tokens. Actual costs vary with usage patterns, prompt caching, and batch discounts. Always verify against official provider pricing pages.