Everyone wants to be compensated for their work - wealthy or not. Just because he's wealthy a company should give him half of what he deserves?
He didn't deserve that bonus. Maybe some misleading half-promises were made, but mr. Salem should know all about those kind of tricks, being an expert trader and all.
Also, no single person can generate 7 billion dollars of worth all by himself, that's insane. You either need a lot of talented coworkers or a shit-ton of capital to work with. Because he worked at GS, he probably had both at his disposal.