You might have the wrong idea about selling high.
Wanting to move one of your players at the height of his value isn't a damning indictment that he's playing over his head—just that right now, you might be able to get more in return for him than you ever will again.
A lot of the players on this list will have adequate to awesome seasons this year, but in fantasy baseball, you can always do better. Instead of hanging onto who you have through better or worse, why not just take the better and let someone else deal with the rest?
(Tell me that isn't a deal you'd like to translate to another aspect of your everyday life.)