Most AI vendors sell you one model at a flat fee. It works — until it doesn't. Here's the pitch: "Unlimited AI, fixed price!" Under the hood, they've slapped a single budget model on everything — your customer support bot, your code reviews, your data analysis, your document generation. It handles the simple stuff fine. Then you ask it to reason through a complex business decision, and it confidently gives you an answer that's completely wrong. You go back to the vendor. Their response? "You need to upgrade to the premium model." That's not an upgrade problem. That's a model selection problem — and you just paid to discover it the hard way. Choosing the best LLM for each task is an architecture decision, not a shopping decision. LLMs are not interchangeable. Each model family is built with different strengths, different architectures, and different cost profiles.…