According to Steven A Smith the C's told Marbury that if he wanted to win a championship he should give back more money and then sign with the C's so he could help them win. Then he'd make the money up next year. (Not suggesting it would be with the C's)
I still don't understand why anyone (from fans to Ainge) would think that a guy who is willing to put his career on hold for an entire season for 2 million dollars is suddenly going to change the way he plays (i.e. become a team player/play D/etc.) But we'll see what happens.