You need a treatment or you'll die. How much are you willing to pay to stay alive? I'd pay everything that I have, because it does me no good when I'm dead. This doesn't depend on how much I have. In fact, I'd be willing to pay money I don't even have yet. This is why so many people go into debt to stay alive in the USA.
Assuming that there's only one person able to save my life, sure. Of course, that's not much of a
market.
That one person is going to make a lot of money... so much that other people are going to want to be able to do what he does. Once there are a suitable number of people willing to save my life, I have choices, and the price will drop. We won't stay alive without food, either... and most of us would have difficulty doing so without housing. Markets are about supply
and demand.
This glosses over a lot of important details, but so does the point being addressed. Possibly a good argument can be made that markets don't regulate health care well... but this isn't it.
This argument doesn't address the most obvious free market predictions.
By the way, if there really is only one person who has the cure for
your disease... be thankful he's there, and that you
do have the choice to give him everything you have in return for saving you. You can still decide not to.