The high cost of a medical school education is offset by the incredibly high return in the form of postgraduate earnings. I don’t think many 60-year old physicians regret their career choice because medical school was too expensive.
Perhaps an unintended consequence of free (or super low-priced) medical school might be lowered salaries for medical professionals. While some medical professionals are driven solely by their desire to aid others, many others are driven by their desire to earn a large paycheck. Not that there is anything wrong with pursuing a career because one wishes to earn money.