It's possible that my view on a variety of things could change post graduation or residency. Similar to what Q has mentioned, it's likely that I will see and learn many things that I could not have anticipated. However, anticipating that which I truly cannot know is out of my control. My goal when making big decisions is to consider this question: Did I make make my best effort to investigate and find all the relevant information that I could, and did I make a logical objective decision using this information? So long as I was painstakingly thorough and objective in my decision making, I seldom ever feel remorse or regret for decisions that I make.
This very much means making plans A, B, C, D, E, and F. I spent months making my decision for a reason. That process involved researching schools, contacting and speaking with professors at schools, speaking to current students, researching repayment plans and financial information, researching various career options (academics vs policy vs business vs private practice, etc), speaking with people in different professions, speaking with people who quit/delayed/turned down medical school, and looking back on my previous choices to make sure that I wasn't repeating mistakes I've made in the past or ignoring important lessons. If after the end of all this I make a choice and later think to myself, "Dang, I really didn't need to pay >$200,000 to go to this school", all I can do is shrug my shoulders and accept that I did my best to make an objective reasoned decision at the time. Even accounting for this eventuality is one of the things that I considered, and I had to do my best to assign that hypothetical scenario the proper weight (i.e. "If my plans change, how damaging will the lost flexibility of owing money be? What sort of career or lifestyle options will be sacrificed? How much do I value those career or lifestyle options and am I comfortable with the possibility of losing out on them? Etc").
It's not easy and it's a decision that I hope few people take lightly. But if one is thorough and objective, I absolutely think that for some people simply paying the money will best serve their interests at particular schools.