Mike Lombardi was on with Bill Simmons on his show and he made a point so many fans and GM's in the NFL just don't realize.
This is what he said:
He’s trading a guy who is very talented, but very moody, very inconsistent with his effort, and so for him to pay that player that type of money sends a message to the locker room that, look, I tolerate this and I reward this. He’s never doing that. And with Belichick, every message he sends in terms of a contract is a message to the locker room.”
Contracts are messages from ownership that REWARDS BEHAVIOR. Which is why every time to sign a guy from outside the building you are taking a huge risk at showing the locker room behavior (that you don't really know about yet) that you endorse and encourage.
And while off-the-field issues are important (much more so today in our social media world and extreme judgement of all people famous), Belichick mostly cares about "between the lines" actions (and that means anything of or about the team, facility, etc.). Which is why I bet for as much as Aaron Hernandez was a despicable human being outside the Patriot's facility, I bet he was okay at following Belichick's rules and putting in the work heading into games (and backing it up on the field).
If I want to give credit to the Steelers, they know this better than most teams in the NFL. And it's one of the reasons they are a consistently good team. I hope Tomlin doesn't get off this track as the money starts going from Cowher/Colbert players to Tomlin/Colbert players but for the most part it seems like they've picked pretty solid guys to give long-term deals to.
Belichick wasn't going to pay Collins. He is going to reward Hightower, who from all reports, is a consummate professional and does all the little things before and during games. Hightower will get the huge contract and Collins goes to Cleveland, who likely will pay a bunch of money for a "talented, moody, inconsistent effort player" that will send to the entire Cleveland locker room that this behavior is not only tolerated but rewarded (and at the same time undermine all those players that work hard and are looking for 2nd contracts).