I am guessing that NBA team's non-basketball expenses are out of control.
I imagine that is why the players don't like the league's figures.
"In each of the first four years of the deal. probably losses of a couple of hundred million, at least $200 million a year," Stern said. "At our current level of revenue devoted to players' salaries, it's too high."
Basically how it works is that the cap is set at 51% of basketball related income (with some carve outs for benefits, etc.)
With teams spending to the cap, and well beyond in some cases, it's easy to see why things might not be sustainable for the league. Basically, somebody needs to save the owners from themselves, like happened in the NHL.