MOST 24 year olds do waste their money, and are not as dedicated, which is why MOST 24 year olds don't look like pro bodybuilders.
Also, I can't think of many PRO bodybuilders who are only 24 or 25.
And, You don't need to be rich to be a successful bodybuilder. Even with the price of gear, food, etc. its all about priorities. Kai Greene is the perfect example. Lives in a bad neighborhood in New York, has never owned a car, rents a small apartment, etc.
Any and all of the money he has goes to food, supps, gear, etc.
He is aware that he cannot afford everything he needs if he starts buying things like nice cars, nice house, etc.
So, he goes without everything he does not appsolutely need.