The main difference is that healthcare is absolutely not a free market and is pretty much as far from it as it can possibly be. You don't choose your insurance, your coverage, your claims, or even your doctor. It's so bad that your doctor, in fact, doesn't even choose your care - your care is already pre-determined by your insurer's guidelines. Your doctor just sees you for the allotted time insurance grants them, runs the allotted tests they're allowed to run given your symptoms, and then gives a diagnosis and follows the set treatment plan for said diagnosis.

With food or water, if the price is too high I can just go somewhere else. With healthcare, I don't even know the price. And even if I did, I can't go anywhere else. I'm completely at the mercy of the system to be reasonable. So, obviously, the system isn't going to be reasonable.