If I went IM or FM as a MD, I will not be able to pay my loans off (and if I could, it would be by living on less of a take home pay than many PAs). PA and NPs in primary care also have a large scope of practice--> MD isn't worth it that route unless you absolutely want the MD
If I want surgery as a MD, it will suck and I may have to live "like a resident" 5-8yrs after residency, but I can pay it off. The job of a surgical PA and a surgeon are very different--> Worth MD. A surgeon would still likely come out ahead of a PA financially. Non-specialized IM or FM, won't.
So from an investment standpoint, MD is not worth it over PA for primary care (unless you come from money, have a very cheap state school, or get a scholarship)