Low, High and Max, obviously, can't be compared across models. They only mean the model is likely to spend less reasoning effort (~output tokens) with Low than

Low, High and Max, obviously, can't be compared across models. They only mean the model is likely to spend less reasoning effort (~output tokens) with Low than High on the same, *single shot* task. But even in this very post, you can see that Max was actually cheaper than High. If you are using API, you should be comparing based on end-to-end cost or speed or whatever blend of those two matches your cost/time budget.