My son graduated in May 2012, and started to work as a software engineer then. He applied for admission to medical school for class 2013, and got acceptance.
To him, the opportunity cost to attend medical school is about $900k.(Working as a software engineer for seven years will bring about $700k. Cost to pay to medical school will be about $200k.)
My point is monetary reward is not motivation for some people to go to medical school.