The Model Bill Is 30% of Your Inference Cost
A finance lead at a mid-sized AI company told me last quarter they had "optimized their LLM spend" by switching their agent backbone from Sonnet to Haiku. The token bill dropped 22%. The total inference cost per resolved ticket went down 4%. When we pulled the full decomposition, the model line item was roughly a third of the per-request cost. Retrieval, reranking, observability, retry amplification, and the human-in-the-loop review queue ate the rest — and none of those got cheaper when they swapped models.
This is the most common accounting error I see in AI teams right now. Token cost is the line item on the invoice you pay every month, so it becomes the number everyone optimizes. But for any non-trivial production system — RAG, agents, anything with tool use or evaluation gates — the model inference is often 30 to 50% of the real unit economics. The rest sits in places your engineering dashboard doesn't surface and your finance team doesn't categorize as "AI spend."
