Why AI Agent API Costs Grow Faster Than Traffic

AI agent API costs rarely grow in a straight line with traffic. A product can have 20% more users and 200% more model spend, because the expensive part is often hidden inside the workflow: long context windows; tool calls; retries; fallback models; duplicated prompts; agent loops that keep asking for one more step; output tokens that are much larger than expected. If you only check the model's sticker price, you miss the part that actually shows up on the bill. Here is the checklist I use…