The reason you see superstars traded so much is because of the potential ratings out of whack. Most of the superstars have C or even F potential rating, and potential rating is the most important thing to trade value in the game.
I use the Mets in my franchise and tried to trade Reyes for a double A prospect with a A potential rating and the computer had 0 interest even though Reyes overall rating was much higher, but right now his potential rating is F.
The roster update will fix that problem.