There's an interesting rebuttal to this written by someone who is both a Swat alum and another RA at the Fed:
http://www.optimizationprime.com/archives/000063.html

Of course, I have a very different view of grad school from people in the humanities, since science and social science programs sometimes pay much more. But I do agree that you have to be pretty interested in what you're doing to make it through, even if you are making enough money to live on while you do it.