That obvious point is often overlooked. There is no reason why Performance Enhancing Drugs would not be subject to similar YMMV factors as any other type of drug. weather it's chemotherapy, blood pressure medication, antibiotics or herbal digestion aids. The substance can have significant effects, modest effects, make no difference or even make make things worse.
There's probably lots of people getting little to no bang for the buck from their PED's still risking to get caught or suffer side-effects just because of psychological pressure to make sure they're keeping up, or in some cases their coach may feel they need it for their confidence or to remove the idea of being out-juiced as an excuse for not competing hard enough.
I'm sure with a bit of research I could dig up multiple examples from fighting sports where someone has failed PED tests after a fight in which they displayed sub-par form.
