Well, he'd certainly deserve a max contract based on his value, but I'm not so sure he'd get many offers in that range.
He is a [layer who shines on a good team. He isn't flashy enough to sell tickets or a good enough scorer to carry a bad team. And how many good/great teams are in need of a great PG AND have the cap space to offer a max contract? Few if any.
He'd get paid regardless, but you see the crazy contracts to inferior players (Rudy Gay, Joe Johnson) given by their teams, not new ones.
In Gay's and JJ's case, they overpaid as I don't think their were any real bidders (or their talent/impact warrants their paychecks, but that's another story). Would the C's blatantly overpay Rondo to keep him? Maybe, but I doubt it. Ainge did the smart thing and wrapped him up when they did, probably saving about $15 million over the next 5 years.