Read the bill, do the math

The lessons in this chapter are coming. The orientation step you're reading is the placeholder while the interactive content is authored.

When the chapter ships you'll work through:

1. A real model invoice line by line. Per-token pricing, cached vs uncached, input vs output.
2. The four-line cost estimator you run before any deploy.
3. Prompt cache hit rate, why yours is probably under 30 percent, and the prompt reorder that fixes it.
4. Streaming vs batching, with the cutoff that tells you which one wins for the feature in front of you.

For now, read the chapter overview above and come back when the lesson plan goes live.