Sure, the revenue structure based on the assumption "10 guys, most of them hedge fund managers, will make over a billion dollars, guaranteed" seems sustainable.

Most of such income is off one-time events http://www.forbes.com/sites/robertwood/2013/12/20/mark-zucke... You can hope they're repeatable, and that works during the boom years, but during the bust years it becomes a "California double whammy" - not only your projections are over-blown, but the high-income tax events (which tend to be IPOs or big hedge fund wins, judging by the caliber of people stuck with multi-billion dollar tax bills) have also been eradicated by a stagnating/falling economy.