The cost formula (memorize this one)
Every Mistral La Plateforme API call follows the same math. There is no platform fee, no per-call fee, no minimum. You pay for what you send and what you get back, at the model's per-1M-token rate:
``` cost = (input_tokens / 1,000,000) × input_price_per_M + (output_tokens / 1,000,000) × output_price_per_M ```
Unlike OpenAI and DeepSeek, Mistral does **not** currently publish a cached-input discount on La Plateforme. That means there is no automatic 90%-off lever for stable system prompts — if you are migrating from OpenAI and your bill is cache-dominated, model that explicitly when you compare quotes. The compensation is that headline rates are lower across the board (Large 3 at $0.50 input is already 80% cheaper than GPT-5.4 at $2.50, before any cache discounts on the OpenAI side).
Mistral does not bill 'reasoning tokens' as a separate stream the way OpenAI's o-series does. When a Mistral model emits chain-of-thought in its response, those tokens count as normal output tokens at the standard rate. This is simpler to budget against but means you cannot 'see and skip' reasoning trace separately — cap `max_tokens` to keep verbose outputs in check.
The free tier matters at evaluation time: La Plateforme grants up to 50 free monthly requests per account, enough to prototype against every tier in the table before you ever attach a card. Use it to confirm Small 4 hits your quality bar before you default to Large 3.