What are your goals?
An MPA can be very useful for the quantitative curriculum in particular the stats and econ which you may not find in a law program. Harvard's Kennedy School says that MPP graduates might expect around $60K upon graduation. If you're a lawyer going into white-collar crime prosecution, for example, it could be a complementary skill-set. An MPA would help a lawyer understand implementation of the law. A lawyer would argue in the Bakke case, an M.P.A. at the University of California might be tasked with implementing the judge's decision. Public policy degrees are fairly flexible so they are advisable only so far as your interests are defined.
I appreciate your skepticism since it is expensive and two years. We all need to pay bills and I understand that. Here's a good rule of thumb though: If money motivates you more than the service element, you're barking up the wrong tree. Stick to white-shoe law firms like Akin. Public policy programs are more idealistic than are legal ones. Charlie Rose, for example, went to law school and dropped out because he found it chilly and destructive.
