# Cost per useful answer

> Cost per useful answer: Total spend divided by answers that were both on time (met the SLO) and correct. Retries, late replies and wrong answers all…

Canonical: https://llmdojo.dev/glossary/cost-per-useful-answer

Also called cost per useful output.

Total spend divided by answers that were both on time (met the SLO) and correct. Retries, late replies and wrong answers all raise it.

Learn it in the lesson: [Cost per useful answer](https://llmdojo.dev/learn/inference-optimization/cost-per-request/useful-answers) (Inference and Model Optimization · Cost per Request and per Useful Answer).

## Interview questions about Cost per useful answer

- [(Illustrative numbers.) Model A costs $0.004 per request and is correct 50% of the time; model B costs $0.006 and is correct 95% of the time. Which is cheaper, and what should you track?](https://llmdojo.dev/interview/q/illustrative-numbers-model-a-costs-0-004-per-request-and-is-correct)

## Related
- [Cost per request](https://llmdojo.dev/glossary/cost-per-request)
- [Batch API](https://llmdojo.dev/glossary/batch-api)
- [Utilization](https://llmdojo.dev/glossary/utilization)
- [Glossary of every term](https://llmdojo.dev/glossary)