Speaking of the whole picture... For obvious reasons I've stayed out of this thread and will continue to do so. If you believe the Blackhawks should have kept Campbell, that's your opinion and you're welcome to state it. But I've seen this math used a few times now with no response and can't resist jumping in.
First off, the d man who really 'replaced' Campbell in terms of role/minutes was Nick Leddy. Montador, in turn, 'replaced' Leddy.
But fine, ignore that... Add up what the Blackhawks owe or would have owed Olesz and Montador (whose cap hit is not $4 million, FYI)... and why not, go ahead and throw in Oduya's full salary for the season just for kicks... you'll find Campbell is still more than $10 million higher. You can't focus on one year and ignore all the others remaining.
Plus, Olesz is in Rockford and not actually counting against the cap. When you factor that in, it's obviously closer to $20 million.