You have to account for all the money you already paid him when you cut him. For example, his signing bonus, it was already paid then spread out for the cap. When you cut him it all escalates to the moment you cut him. That comes out to over 40 mil.
There is also a guaranteed salary that he must get paid (10 mil).
So you "save" the 50 mil cap figure but gain 50 mil in dead money. So you save nothing and are still 60mil over the cap.