How to fix: LLM API bill is unexpectedly high
Cause
Spend is invisible by route, so an expensive prompt, oversized context, or a background job is quietly driving most of the cost.
The fix
- 1Instrument every call with tokens, latency, and cost tagged by route and model — you can’t cut what you can’t see.
- 2Find the heaviest routes and right-size the model: move low-stakes calls to a cheaper tier behind an eval.
- 3Add prompt caching for large stable prefixes and provider prompt caching where available.
- 4Move non-urgent work to batch APIs and trim oversized context (retrieve, don’t stuff).
- 5Add fallback chains so timeouts don’t trigger expensive retries on your priciest model.
Prevent it
Keep a live cost-by-route dashboard and gate prompt/model changes on evals so savings don’t silently erode.
Frequently asked questions
What causes “LLM API bill is unexpectedly high”?
Spend is invisible by route, so an expensive prompt, oversized context, or a background job is quietly driving most of the cost.
How do I prevent “LLM API bill is unexpectedly high” from recurring?
Keep a live cost-by-route dashboard and gate prompt/model changes on evals so savings don’t silently erode.