The formula
Cost per developer = sessions/month × calls/session × [ input × (1 − cache%) × input price + input × cache% × cached price + output × output price ] × (1 + retry%). ROI compares this with hours saved × developer hourly rate.
Questions
How much does an AI coding agent cost per developer?
Typically tens of dollars per developer per month for moderate usage, more for heavy agentic workflows. Prompt caching of codebase context cuts this substantially.
Is a subscription or API cheaper?
For light, steady usage a flat subscription is often cheaper and simpler. For heavy usage it depends on volume — compute the API cost here and compare to the subscription price.
What productivity gain justifies the cost?
Because developer time is expensive, usually just a 1–3% gain. This calculator computes your exact break-even productivity percentage.