I am trying to understand what you mean by "public good". It's not the formal economics meaning (https://en.wikipedia.org/wiki/Public_good), because healthcare clearly is excludable and rivalrous.

The notion of a "public good" also isn't about how things should be treated, but more about how things necessarily are.

It sort of seems you're making an argument unrelated to economics here, even though it's using words also used in the jargon of economists.

Nope, I'm using exactly as intended.

If one is to believe that healthcare products should be subject to market forces, then their prices should be variable in the same way other products are. In which case the answer to the question is, yes someone with a "niche" health problem would pay a substantially high price.

If however one believes that healthcare should not be subject to market forces, that is, it should be available to all equally (non-excludable) and cannot incur asymmetric costs between users (non-rival) then the answer is no, it would not be good.

The important thing about public goods is, you can't exclude them if you tried. By saying we should pretend that healthcare is a public good, you are saying we have a choice in the matter. This on face makes it a non public good.

This is a fine opinion to have, but you do yourself no favors by misusing jargon like this.

The problem with healthcare is that it's often not negotiable. Let's say you're a billionaire in a world with zero privacy. You get cancer. One company owns the patent on the drug you need to survive. Is it okay for them to charge you a billion dollars for treatment?