Good question, I wish I had a better answer.
In my limited experience, I could only say that no matter the field, it will take a while to pay off. Except in the instances where employers will pay for you to get your MBA while you work for them full time. That's a pretty sweet deal, and lots of big companies do it.
There are definitely better ways to pull down a 6 figure salary. Becoming a doctor takes that extra special je ne sais quoi.
NS