They will do what makes them money.
If paying boosters ends up being good for the bottom line? They'll keep right on doing it.
If it doesn't? They'll stop and try something else.
I agree with you, based on what I know. The money being spent on boosters would be better spent on upping the amount we all get paid when folks read our work.
After all, I can't boost and my work has only been boosted twice.
But I don't have the whole picture or know the whole story. Nobody has shown me the numbers and nobody will.
So I will continue to write what I want to write, whether or not I get paid big bucks for it, which is what this place is great for.