Why I Built an AI Model Router (And Why You Are Probably Overpaying 100x Right Now)

It started with a $47 API bill. Not for anything impressive. Not for training a model or processing a million documents. Just... a chatbot. A customer support bot for a side project that handled maybe 200 conversations a day. $47. For a chatbot that mostly answered "what are your opening hours?" and "how do I reset my password?" I stared at the Anthropic billing dashboard and had that feeling every developer knows — the one where you realize you've been doing something incredibly stupid for weeks and nobody told you. The Ferrari Problem Here's what I was doing: sending every single user query to Claude Opus. The best model. The most expensive model. For everything. "What are your opening hours?" — $0.025 "How do I reset my password?" — $0.025 "Can you architect a distributed event-driven payment system with CQRS and saga patterns?" — $0.025 Same price. Same model. Every time. That's like taking a Ferrari to buy milk. Sure, it gets you there. But a bicycle works just as well and costs n