$15M and a free agent in 6 months' time is not any kind of discount. Again, Clowney is not going to be the difference for Philly this season. Seattle makes a little more sense, but the cap space is still a significant opportunity cost and it sounds like there are multiple players involved.
By discount, I was referring to trade compensation. Earlier in the offseason, it would have cost considerably more to acquire Clowney.
You made my point for me, it's a one year deal. If a contending team can fit him under its cap, what better place is there to spend the money, at this stage, than on an elite edge defender?