It usually isnt unless the person using is very experienced in the gym and kitchen and has good guidance from others who have used before (pertaining to changes to make in training while on AAS).
Many people gain the most in a first cycle because of the law of diminishing returns. Even on AAS a person can only get SO big.
oh you said same amount of drugs? Well if someone is over their natural potential then it will take a certain amount of drugs to maintain that. And the more muscle gained over the genetic max means more drugs needed simply to maintain it (at the same body composition).