Nope. Not underpaid at all. The Yankees are not going to allow Jeter to play his last year or years playing for some crap organization like Oakland.
This is like the Lincecom deal, it's the face of the New York Yankee franchise. Not everything in life is "fair" and "equal" for everyone. Jeter gets special treatment from the Yankees and will for the rest of his life.
But if he has another injury wasted year, he should retire as a Yankee in 2014.