Maybe if there is a red flag deal where players are exchanged between teams for over market value (which is tough to define in cases of the highest end players I imagine) the players should be made free agents, and the money lost forever. This would end trading pretty abruptly. I don't know how big a problem it is or how seriously the BB's/GM's are about containing it, but removing the players in question from the teams in question would probably halt the activity.
Once I scored a basket that still makes me laugh.