I also disagree with the OP in that the players have no risk or liability whatsoever. They're giving up their bodies, and shortening their life expectancy in the process. For guys like Big Baby, Rondo, DWest who go all out and hit the ground every play, they're pretty much asking to be injured.
And don't say "anybody can get injured", that's way different, most of us aren't putting ourselves in harm's way on a daily basis.
There's even guys like Reggie Lewis who gave their lives for the game. I can't see how risking money automatically trumps risking your body. Even if the owners lose every penny they spent on the team, at least they're guaranteed their health.