Instead of handy metrics, how about architecting software properly in the first place? I’ve seen use-cases for AI which don’t need AI, at least, not as a first resort. They could, for example, use an expert system to refine the request for the AI (and possibly even provide an answer without requiring the AI, and all the compute that that entails, at all) before passing it to the AI.
But efficiency isn’t really a watchword of computing these days. For all their other benefits, modern languages (pretty much anything (not quite everything though) including and since Java) aren’t efficient. They’re safe, yes, they’re easier to develop for. But they aren’t sympathetic to the available resources of the computer.
So yes. It’s an important consideration. But it’s not the only consideration.