cost-check.txt
Here is what I'm building: <describe, including anything that calls a
paid API or model>

Estimate the monthly cost at 10 users, 1,000 users and 100,000 users.
Show the arithmetic so I can check it and change the assumptions.

Then:
- Which line grows fastest, and what makes it grow?
- What's the cheapest change that halves the biggest line?
- Where could a bug or a bored stranger run the bill up, and what
  limit stops that?

The last question is the one that matters. Unmetered API calls behind a public form is a way to fund someone else's project with your card.