The Jazz got him for Koufous (does he count as a prospect?) and two firsts.
So Dallas probably would have had to give up RoddyB, JJ Barea, Dampier and picks.
Jefferson is probably a more valuable player overall in a vacuum, but he sure can't control the pain the way Tyson does on defense and I think that is what Dallas really needed.
Then again, who would turn down a post that can push out 23 and 11 for a season?
Tyson's defense and Barea's offense would be a lot to lose from this playoff run.