Apples and Oranges
There's only one QB on the field and if you have a franchise QB, the other QB (barring injuries) is entirely useless.
D-linemen, OTOH, comes in 3's or 4's on any given play, depending on the front, heck you can even play with 5, and Williams is a kid who offers scheme versatility, he can play end in any scheme and D-tackle in the 4-3, so there's plenty of ways to get him on the field, even with the talent we had on the D-line to begin with.
...so the Jets are going to tie up 1/3rd of the salary cap on 3-4 DEs...okay. $50 mill of cap space to these 3 fellas. Works for me. Just better hope we never find a franchise QB and stay mediocre so we can keep them together!