AI Evals in Practice

Chapter 11 — Cost and Latency of Eval Pipelines

Running evals is not free. Every LLM-as-judge call costs tokens. Every embedding comparison costs an API call. Every production sample that goes through the scoring pipeline consumes compute time. And if you are not careful, the cost of evaluating your system can exceed the cost of running it.

This is not a hypothetical problem. I have seen teams whose eval pipeline cost more per month than their production LLM spend. They built thorough evaluations — LLM judge on every request, full faithfulness checks on every RAG response, multi-criterion rubrics with detailed reasoning — and then discovered the monthly bill. The eval pipeline was silently costing more than the feature it was measuring.

In this ...