It's all homebrew crap for the most part. Sometimes brewed in compounding pharmacies or whatever, but it's still the same Chinese raw material.
It's not just a money issue. And even if it was, many well off people are cheap as shit anyway and try to save a buck.
I think when a movie actor (Reynolds, Wahlberg, The Rock, etc.) want to get in shape for a movie, they can just go to a doctor that writes scripts for celebrities who want it. The WWE guys definitely get their stuff from Dr's the company bribes to give them gear.
So I mean, maybe that may be true of the pros but if so, the underground crap must be good if they get so fucking huge.