That pretty much sums up what Gambo said above. He said the Suns aren't looking to add payroll and any trade that included Garnett does just that.
Gambo is actually totally clueless about stuff like that. A KG trade for example wouldn't really add to the payroll.
Sure Gambo thinks that the extension Garnett will get will start at the same money he already is making right now while Garnett will obviously whereever he goes take a considerable paycut in his extension.
Nevermind if you stay at the same payroll you are already at and replace Marion with Garnett, you are obviously going to increase ticket sales and whatever..
Considering the volume of this trade (the 125% rule) the Suns could also give up more salary than they take back.
Example: (works under the cap)
Marion, Diaw, Barbosa (~31M$)
for Garnett (22M$) not considering trade kickers which I believe Garnett could waive anyway. Now even if you threw in Garnetts trade kicker however high it is, the Suns still save a TON of money.
The Suns would save 9M$ right away next season. Then you sign Garnett for an extension 4 years/60M$ that would start 2008-2009 and Thomas expires, shaving another 16M$ off of the cap.