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Lab
API token cost for a month of coding-agent use, next to the subscription price.
API bill $48.80 for 80 sessions on Claude Opus 5.5. The cheapest plan is lower than the API bill by more than 10%.
Subscriptions have usage limits this calculator cannot see. If you would hit the limit and keep going on credits or the API, the plan is no longer a flat price.
Still Building
Sessions are working days times sessions per day. Cached input is that share of the input tokens. The rest of the input is billed at the full input rate. Output tokens are billed on their own. The API bill is those three added up for the month.
The comparison uses the cheapest subscription for the same vendor. API is cheaper when the bill is under 90% of that plan, the subscription is cheaper when the bill is over 110%, and they are about equal in between.
Every rate below was read on the vendor's own pricing page on 2026-09-26. Claude rates use the standard tier, not batch or fast mode. OpenAI's faster gpt-5.3-codex tier costs twice the standard row and is left out. Cache writes are not modeled; a cache write costs more than a plain input token, so a heavy first turn is slightly underpriced here.