I think you're overlooking a couple of things:
1. If Cobb is a Post-June 1 release (which GB would probably do), his dead money gets spread out over 2017 and 2018 ($3.25M/each) which isn't very significant considering the growing cap.
2. GB will need to spring a decent amount of money to retain some of their guys, if they want to bring back Nick Perry, that could end up costing them about $8M/year (if not more, he's maybe the top FA pass rusher considering his age and production) and trying to bring back T.J. Lang could cost them $7M/year (based on the Sitton Contract).
I'm not saying it's overwhelmingly likely to happen, but the Packers did just cut Josh Sitton to save about $6M, and they didn't even have the depth on the OL that they have at WR. I definitely think they'd consider that move if there is a free agent they like (considering their need at CB, and the CBs going to UFA, I'd bet they'd like to grab one if they can).