> cheapest AI model when asking questions and then switch to the more expensive if it doesn't work.

The thing is, more expensive isn't guaranteed to be better. The more expensive models are better most of the time, but not all the time. I talk about this more in this comment https://news.ycombinator.com/item?id=42313401#42313990

Since LLMs are non-deterministic, there is no guarantee that GPT-4o is better than GPT-4o mini. GPT-4o is most likely going to be better, but sometimes the simplicity of GPT-4o mini makes it better.