I keep wondering the same thing. The market is now dried up.
I don't know there are still a couple of guys that we might be able to get for dirt cheap that have something left in the tank:
Michael Johnson had 17.5 sacks between 2011-2012, he's had 2 subpar years in a row, but might be able to rebound if put in the right program, and will likely come cheap.
Adrian Clayborn was really good in college, but hasn't be able to stay healthy in the pros. Might be worth kicking the tires there.
Kroy Biermann isn't much in pass rush, but is pretty good as a run stopper, and probably an upgrade over Spencer.
John Abraham is a sack machine who missed almost all of last year with concussion issues, with the right contract it might be worth kicking his tires and have him rotate in.
Without much looking I came up with those guys... all DEs... all COULD add something to our system for the right amount. I think at this point the Cowboys are just looking to get diamonds in the rough, and don't want to risk finding some coal in a diamond mine... or something like that.