The Cost of 10 + 10

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A solar-powered calculator adds 10 + 10 for nothing. Daylight hits the photovoltaic strip, a few logic gates flip, and the display reads 20. No per-use cost, no subscription, no network round-trip, no telemetry. Send the same question to a hosted large language model and the model is not really adding — it is generating a probable string of text one token at a time, and every token is metered. The table below is what 10 + 10 actually costs when the answer comes from a model.

# Step Input tokens Output tokens
1Load the platform system prompt~2,500
2Load tool / skill / connector definitions~3,000
3Load conversation context (turn start)~80
4Tokenize the user prompt "what is 10 + 10"7
5Forward pass through every parameter of the model to produce the first output token(replays the input above)
6Emit internal reasoning / "thinking" tokens~120
7Generate the answer token: "20"1
8Detokenize, stream, persist, log to telemetry, bill
Total ~5,587 ~121

At a current frontier-tier rate of roughly $15 per million input tokens and $75 per million output tokens, that single sum costs about 9.3 cents. The calculator costs zero. Ten employees asking the model ten times an hour for an eight-hour day works out to about $74 a day to reproduce what a $4 piece of plastic from 1985 does silently on a windowsill. The model is doing extraordinary work elsewhere. Addition is not it.