I'd say that it doesn't matter if the wages are inflated - as long as the wages aren't deflated, everything will be fine. Even if doctors got paid exactly the amount that a perfectly efficient market would predict, that would still be quite a large amount.

By the way, make sure he talks to a good adviser. To my knowledge, as long as you take certain classes (Calc, O-chem, etc) you can get into medical school without a biological science degree. As for graduate school, my impression is that people in computer sciences are typically very well received in many biological contexts (bio bioinformatics, bio engineering, etc). There are many biologists who can't code and would love a grad student who can. There's a possibility that your friend need not bother switching majors and should just hurry up and graduate, go straight into bio-grad/med