For the 2006 season, he made $12.25 million.
For the 2005 season, he made $22 million.
He obviously doesn't need the money he can made by pitching another season, so maybe it's not.
But even if it is, so what? The Yankees offered him $28 million for one more year, why is he a bad person for accepting that? They offered it to him. I'm presuming that if someone offered you $28 million, you wouldn't hesitate at taking it. It's his job; he's making money.
Is it too much? Yeah. But they offered it, and he'd be stupid not to accept.
"One no longer loves one's insight enough once one communicates it."
The opposite of creation isn't war, it's stagnation.