Guide · Cost Control
Why Is My AI API Bill So High?
Your OpenAI, Anthropic, or Gemini bill spiked. Here are the most common causes—exposed keys, abuse, inefficient prompts—and how to fix them.
Surprise AI bills are a Cost Optimization gate failure—ceilings, attribution, and loop bounds. Primary control: Cost Optimization
Tokens meter every request
AI spend scales with volume and prompt size, not just "how many users." High bills usually mean a leaked key, a retry loop, missing per-tenant wallets, or growth without caching—not mysterious vendor math. A marketplace bot retried a failed embedding job with no backoff; the same 40k-token batch ran hundreds of times overnight. Finance saw a mid-five-figure line; engineering found it by correlating `request_id` with vendor usage.
Cut cost where it actually forms
Custody — keys only on a backend proxy. Budgets — per-user / per-tenant token or request caps that reject when empty. Efficiency — smaller models where quality allows, cache identical prompts, trim context. Signal — provider spend alerts plus your own usage by feature/endpoint.
Hard retries and spend alerts stop the next overnight loop before standup.
Treat cost as a production gate
APRF Cost Optimization wants ceilings and alerts you can show an assessor—not a postmortem after the invoice. For sudden spikes, triage keys first; for chronic high spend, fix wallets and prompt waste.
Next: Cost Optimization
Open the related pillar specification for mandatory checks, artifacts, and pass conditions. Self-attest is optional.
Related
Frequently asked questions
- Why did my OpenAI bill spike?
- Common causes: exposed API key (in frontend or public repo), abuse or scraping, a bug causing repeated calls, or scaling usage without limits. Rotate keys if exposed and add rate limiting.
- How do I limit AI API costs?
- Use a backend proxy for all AI calls, set per-user rate limits, enable billing alerts, and monitor token usage. Choose smaller models where possible and cache responses.
- Should I put my OpenAI key in the frontend?
- No. Any key in frontend code can be extracted and abused. Use a backend server to hold the key and proxy requests. This also lets you enforce rate limits and usage controls.