I think this fiscal responsibility is overrated by some on this board. We're not the Red Sox and we're not the Patriots. Because of the nature of their leagues, fiscal responsibility has more incentives. In the case of the Red Sox where they have no salary cap to work with, if they let a guy like Johnny Damon walk, they can go out and sign another superstar easily. That's not the case with the Celtics. Yes, they'll have the midlevel to use on someone else, but who can take Posey's place for next year? And don't give the splitting the midlevel B.S.; quantity is not superior to quality in the NBA. Only 5 players can play at a time.
In the case of the NFL, you need 22 starters plus special teams and backups to be effective. You only need 5 starters and 3-4 solid backups to be good in the NBA. To make a stand on one player's salary makes sense when he's just 1 of 30-40 players who matter. It's a bigger deal with James, when he's 1 of 8-9 players that matter.
Furthermore, when the Sox and Pats have taken a stand and not paid players, they've had the luxury of time; they could afford not to win it all the following year if they could come back and win it all the year after. The Celtics don't have that luxury.
Right now if it's the difference between 3 and 4 years, Danny is a fool to pass on Posey. The C's won't have cap space anyway once they re-sign Rondo, so they might as well bring James back to make a run at #18,