LLM Load Testing Can Cost Thousands With No Native Test Mode From Providers

Engineering teams building on LLM APIs face steep costs when running load tests, as every call to a live endpoint consumes real compute and burns real budget. A scenario with 1,000 concurrent users making three LLM calls each can generate 1.8 million API calls in just 10 minutes, resulting in bills that are hard to justify internally. The problem worsens with tool-augmented calls — web search tools can inject 30,000 to 40,000 extra tokens per call, often doubling actual costs versus initial estimates. No major LLM provider currently offers a native test mode that exercises the HTTP stack without running inference, leaving teams to rely on imperfect workarounds. Common alternatives include local proxy stubs and recorded traffic replay, each offering cost savings but failing to fully replicate real provider behavior such as rate limiting.