I'd imagine Floyd would have to be up there but his talent does play a part in his success. Brandon Rios is probably the latest example of a good B+ fighter who got a win thanks to his connections. Who else has been managed well? As in Reward >= Risk.
Andre Berto was the first guy to come to mind for me, made a lot of money without really fighting decent opposition.
I think HBO lost some money with his ass. Dibella got Berto a really good deal but Berto barely got anyone to watch his black ass.
Can't agree with Calzaghe, his late career proved he could have done more earlier and finished with a better resume. That said time will only increase the value on his '0'. Has to be all those fighters who are clearly limited but manage to retain either a belt, credability with the fans or some other factor that means they can keep beating trash and earning money. Arreola would be a good example, Tua another. Both get way more coverage, credability and therefore money than their record justifies.