The amount of data matters right? Also, some level of potential benefit of the application of the optimization. I wouldn't optimize something that only one person uses unless they're time is worth about 1000x mine.
What you describe are RoI (Return-On-Investment) calculations. In business, for every investment you have to be sure that the value is greater than the costs, either if it is a new homepage, a new production machine or a fancy ML optimization.
So I would not say that this aspect is ML specific, even though it is very important.
So I would not say that this aspect is ML specific, even though it is very important.