Mistral Small 4 vs GPT-5.6 Luna
GPT-5.6 Luna passed more tasks on the AIGROW small-business benchmark and Mistral Small 4 has the lower list price, so pick GPT-5.6 Luna for accuracy and Mistral Small 4 for cost. Mistral Small 4 passed 4 of 20 tasks and costs $0.15 in and $0.60 out per million tokens; GPT-5.6 Luna passed 16 and costs $0.20 in and $1.20 out.
AIGROW credit covers Claude Opus 5.5, Claude Fable 5.2, Claude Fable 5.1, GPT-6 Astra, Claude Sonnet 5.5, GPT-6.1 Sol, GPT-6.1 Terra, Grok 4.7 and Gemini 4 Argon. GPT-6.1 Sol below list price
$25 a month brings $110 of API credit and cancels any time; $25 once buys $100. For long documents, GPT-5.6 Luna reads up to 1.05M tokens at once and Mistral Small 4 up to 256K. US dollars, standard rate, shortest context band. Cost per pass from the AIGROW small-business benchmark. Newer model: GPT-6 Luna
- Mistral Small 4
- $1.33
- Tasks passed
- 4 of 20
- GPT-5.6 Luna
- $0.677
- Tasks passed
- 16 of 20
AIGROW small-business benchmark, failed runs included.
Mistral's open-weight small model against OpenAI's GPT-5.6 nano tier, both near the bottom of the price range. GPT-5.6 Luna costs $0.677 per 1,000 passing answers on the AIGROW small-business benchmark, Mistral Small 4 $1.33. 1,000 support replies cost $1.08 on GPT-5.6 Luna and $0.69 on Mistral Small 4, so GPT-5.6 Luna costs 57% more.
What each one costs
The API price per million tokens and the cheapest app plan with each model, from the makers’ own pages. Each name opens that model’s full price page.
- Mistral Small 4
- On the Mistral API, Mistral Small 4 costs $0.15 per million input tokens and $0.60 per million output tokens. Vibe has a free plan and paid plans from $14.99/mo (Pro); the plan list does not name Mistral Small 4. Plan prices read 22 October 2026.
- GPT-5.6 Luna
- On the OpenAI API, GPT-5.6 Luna costs $0.20 per million input tokens and $1.20 per million output tokens. In ChatGPT, the cheapest plan with it is Plus at $20/mo. Plan prices read 22 October 2026.
Side by side
Each maker’s published rate for its standard tier. Cached input is what a repeated prompt prefix costs once the provider has stored it.
| Fact | Mistral Small 4 | GPT-5.6 Luna |
|---|---|---|
| Maker | Mistral | OpenAI |
| Tier | Small and fast | Small and fast |
| Input, per M tokens | $0.15 | $0.20 |
| Output, per M tokens | $0.60 | $1.20 |
| Cached input | $0.015 | $0.02 |
| Context window | 256K | 1.05M |
| Released | 16 Mar 2026 | 9 Jul 2026 |
| Weights | Open weights | Closed weights |
What a job costs on each
1,000 runs of each job at the two list prices. The gap moves from job to job because the models price input, output and cached context differently.
| Job | Mistral Small 4 | GPT-5.6 Luna | Cheaper |
|---|---|---|---|
| Support reply3,000 in, 400 out. | $0.69 | $1.08 | Mistral Small 4, 36% less |
| Document summary25,000 in, 1,000 out. | $4.35 | $6.20 | Mistral Small 4, 30% less |
| Agent task80,000 in (70,000 cached), 3,000 out. | $4.35 | $7.00 | Mistral Small 4, 38% less |
The token counts are ours, chosen to look like real work; the prices are the makers’. A model with no published cache price bills the agent task’s repeated context at its full input rate.
The small print
What each base rate leaves out, from the makers’ own pages: surcharges, discounts, promotions and cache pricing.
- Mistral Small 4
- Mistral Small 4. 119B total, 6.5B active parameters, Apache 2.0. Batch 50% off. Mistral’s pricing page
- GPT-5.6 Luna
- Nano tier of the 5.6 family. Price cut 80% on 2026-07-30. Requests above 272K input tokens bill 2x input and 1.5x output ($0.40 / $1.80). Cache write $0.25. Batch and Flex 50% off. Data residency adds 10%. OpenAI’s pricing page
Other comparisons
Every head to head on the list that involves Mistral Small 4 or GPT-5.6 Luna.
Compare Mistral Small 4 and GPT-5.6 Luna with 52 other models
The price list sets every model’s input and output price side by side, with what a support reply, a document summary and an agent task cost on each.
Prices checked 12 November 2026