The "bill" that people get doesn't reflect what the doctor gets. A bill for $138 doesn't mean either that the insurance company gives the practice $138- often it is $50 or less.
When I worked at our local university/medical school, the bill for an ablation that I did was $100,000. Wow! I got maybe $300 for my 3-4 hours of work. I have no idea where that $100,000 went.
My point was simply that, like most fields, being a doctor isn't as lucrative as it might look or as it was in previous years. My friend's son is going to a private medical school in NY- it's $75,000 a year! For 4 years. That's alot of money to pay.