Yes, the determining factor is: money talks--the more money a guy makes, the more power he has to make more. Jimmy was like a crew chief in Goodfellas/Wiseguy even though he could never be made.
One historical note: the NY families agreed to "close the books" on making new Mafiosi after a scandal in the Fifties in which a high-ranking Mob guy took bribes to "make" men. So the families had to use lots of unmade "associates" like Jimmy and Henry.
One of the great things about Donnie Brasco is that it shows you just how boring and unremunerative life in the Mafia can be. What's it worth to be "made" if you're breaking parking meters for a living?
