Renting Intelligence: A CFO's Mental Model for LLM Spend
Most finance teams filed their first LLM bill in the wrong drawer. It arrived during the experimentation phase, when a handful of engineers were prototyping with an API key, and it looked like exactly what it was at the time: research and development. A few thousand dollars a month to figure out whether the technology worked. So it went into R&D, mentally and sometimes literally, and nobody thought harder about it.
Then the feature shipped, usage climbed, and the same line item that was a rounding error in Q1 became the fastest-growing cost on the cloud invoice by Q4. The problem was never the dollar amount. The problem was that the cost had quietly changed categories — from a fixed bet on building something to a variable cost of serving every customer who used it — and the mental model hadn't moved with it.
That misclassification is the single most expensive accounting mistake in AI products right now, and it's not really an accounting mistake at all. It's a forecasting one.
