My answer to OP's question: Too much, and enough for several attorneys to approach me about potentially trying to eliminate that debt with an adversary proceeding (my alma mater, as well as, one of my lenders have been successfully sued by others for "predatory lending." I'm currently not interested in suing partly because it seems as though that kind of a lawsuit could prevent me from getting funded in medical school...)
Other: I recently talked numbers with a lawyer who said it took her 20 years to pay off $100k of debt from law school while making a $200k/year salary. I wish I could find actual true examples (not slanted "brag stories" but just real life stories) of how long it took real doctors to pay off their typical medical school debt of $250-$300k plus up to $100k of undergraduate loans. Other details and variables aside, I think that seeing how long it takes most people in reality would be telling.
(NO SPECULATION, just a survey of how much they owed, and how long it took (period).)