LLM Cost Routing Cuts Inference Spend 48x and Fixes Broken Margin Curves

A software team discovered that one frontier AI model was handling 77% of their calls and consuming 97% of their inference budget simply because it was the default setting, not because most tasks required it. After measuring a week of production traffic, they found their average call cost $0.00524 on the frontier model versus $0.00011 on a capable open-weight alternative — a roughly 48x difference. Under a $20/month subscription plan, routing all calls through the frontier model turned high-engagement users into a financial loss, while task-based routing kept margins above 97% even at 5,000 messages per month. The key insight is that smart routing does not merely reduce average costs — it reverses the marginal cost curve so that heavier product usage compounds profit rather than loss. The team cautioned, however, that a cheaper model requiring multiple retries can quickly erase those savings, making reliable routing logic essential.