That's true but remember that BB doesn't seem to tolerate malcontents or players that will give him some problems.
He had all the leverage with Collins, but dealt him mid season during a Super Bowl run for a third round pick. That's it.
None of us knows if Butler is, or will be, a malcontent. Or if he will give BB problems if he is "forced" to play for the Pats under the $3.9m tender.
But it Belichick (whose opinion is the only one that matters) THINKS that could happen, he's quite likely to trade him away, even if it means getting less than what he SHOULD get for him.
On the face of it, Collins is worth way more than a third round pick. But BB wanted him gone and if that was the price, so be it.
If he feels that Butler is going to be a problem, he'll trade him away for less than what we think he should get, even though he (BB) had all the leverage.