There were soldiers who were wealthier than some captains, because they were smarter in a business sense. Back in the day guys joined because it was something they believed in, it was in their soul, and it offered more prestige in the underworld. They didn't join to get rich, they were either already moneymakers or they weren't. I wonder though if buying your way in always turn out bad, the Angiulo brothers of the Patriarca Family for example basically bought their way in yet refused to flip when it all came crashing down on them and turned out to be great financial assets to the Family.