Why would Suns have to pay more for Marbury than his last year's 14.5 mil. salary?
Nobody can offer more than the max.
I don't feel like looking at up right now, but it was my understanding that as long as there's a team out there that has the room under the salary cap a veteran player like Marbury would never have to take a pay cut to sign a max contract.
I think Joe Mama is correct, but no team that is that far under the cap is going to offer Marbury a long-term deal starting at $15+ million per year, even if they can. So hcsilla is right that the Suns will be the only team in realistic position to offer Marbury an "overmax" contract.
Unfortunately, I don't think that necessarily means that Marbury will wind up with a regular max-level extension with Phoenix. Look at what happened with Marion. Rather than wait and see what the market would pay, the front office panicked and signed Marion to a huge extension long in advance. And sure, this can be justified by saying that it was a good public relations move, or they didn't want to make Marion angry (as is happening now with Kenyon Martin), or whatever -- but the fact is, that's what the Suns did.
Why will Marbury's situation be any different? Will the front office have the cajones to hold the line on Marbury, the way they didn't with Marion? Or will they use the same rationalizations to make Marbury one of the ten highest-paid players in the league?
It could go either way, but I certainly wouldn't count on Marbury taking a pay cut. He may never even be asked to.