The only problem with this hypothesis is the cost factor. Some guys are always going to be too busy spending their money on training and a place to stay and food to eat to spend any on PEDs. Some of those guys will progress anyway and thereby ensure all things are not equal since they will be ahead in skill of others with equal experience. Then the question becomes, does this person who worked his way up naturally despite being broke ever get motivated to take PEDs? Maybe, and sadly, it probably happens a lot. The more money that comes into the sport, the more motivation there will be to cheat to get ahead. But I hope there will always be a number of guys who just choose to eschew cheating for the sake of their self-respect. Trolls will be drawn to this post like flies to shit for this but I choose to put GSP in that category based upon what I know of his upbringing and work ethic. I know there will always be the smallest shadow of a doubt about every athlete that gets paid, given what we know about PED use these days, but I believe him when he says he will submit to a polygraph test to prove he has never used illegal drugs.
In any case, it's really hard to argue that anyone who thinks they can use without getting caught will do so because of the increasing financial rewards that come from victory. The unfortunate thing these days is that with the USADA testing regimen, I fell pretty sure that you can not get caught if you're willing to spend enough money. To me, that means the guys who are already making the big bucks can continue to use and not get caught while the guys coming up can't afford the good stuff and will only avoid detection by good luck. If they were so inclined, the UFC could take advantage of this to an alarming degree.