Crappy Majors: Math and Physics

I think math and physics are some of the hardest fields to get a PhD degree in. Yet those fields have some of the worst prospects in terms of pay and employment. I remember my math professor told us that a starting salary of a PhD graduate in their department was like 27K (I think he meant post-doc). I personally knew a PhD graduate in physics who was happy to find a job as a car salesman after 7 years in grad school!

Can someone please explain me this? You really have to be "one in a million" to be good in math in physics. I would think that those who are willing and able to do this would be in short supply and would get paid a lot. But this doesn't seem to be the case, right?