1. Layer of indirection created by the entire insurance system, which at this point is clearly not a good model for healthcare. Everyone needs/should have some amount of healthcare, so a system built entirely around the idea that only a minority of people should need to take advantage of the system is silly.
2. The half-assed government intervention of Medicare/Medicaid/ACA/etc – worst of both worlds in that when a government just injects shittons of money into the private sector (without very strong controls on price and behavior), what you end up with is ballooning costs... and that's about it. See also the govt. guaranteeing student loans for another example of the same. Or the Military Industrial Complex. And so on.
One example is with MRI scans. MRI machines, and the technicians and doctors who work with them, are insanely expensive. The US is, of course, not the only country with MRI machines. However, in countries with socialized medicine there may be a much longer wait for people to get an MRI scan for a non-critical issue. What about in the US? If you've got the money, you can get one right away. As a Canadian, I've seen tons of advertisements over the years targeting Canadians for MRIs as a cross-border service.
So the question is: is getting an MRI now instead of waiting 6 months a basic need? Private MRI clinics are definitely profiting from it. It definitely seems frustrating for people on the waiting list who can't afford to cross the border and pay out of pocket. However, it doesn't seem nearly as bad as a company price-gouging people on life-saving insulin, for example.
IMO the problem is more about (very) imperfect competition. Also medicine is very special in many ways (desperate buyers, doctors making decisions for them, moral and emotional weight, etc.), so it's hard to have incentives aligned.