Yeah his value is high, but a playoff team won't offer much in the way of 'useful' pieces. The price at this point should be their top prospects as the draft position won't be very good and their useful players will be kept for the run. During the off season GMs will want to be shuffling their teams around, meaning we have choice, at this point we can only take the pieces they have lying around.
Think of it this way, during draft day, you can target any player, any draft choice or any prospect of your choosing, why do it now when you have such limited trade options to pick from? Not to mention, after UFA day, people who did'nt get the FA's they wanted may pay even higher for him.