Shaq didn't sign here for money: he signed here to stop Kobe from getting six rings, and to get a fifth ring of his own. Shaq doesn't need any more money...the dude's set for life with advertisements and the money he's already accrued.
You make it sound like he was forced to sign with us for the minimum...wasn't Dallas or someone offering him the mid-level exception? He wants to be here, and he wants to win. However, he is 39, and at 39 yrs old and 300+ pounds, you have to take care of your body and save whatever's left in the tank for the games that actually matter (playoffs).