Since we are talking about health, the ultra wealthy are still human beings, they get sick and die like the rest of us.

And they want to stay healthy and live long, also like the rest of us.

It means it is in their own selfish interest to invest loads of money into health, because that is what will help them achieve that goal.

But again, their body is much like our bodies, so every advance in medicine that can help them live longer will ultimately help us live longer. Maybe at first, only the wealthy will be able to get these state of the art treatment, but processes will improve, patents will expire, and sooner or later, they will be available to all of us.

This is one instance where there is no real need to "tax the rich", research is good for all of mankind, the rich are not taking away knowledge from the poor. This is in contrast to natural resources, like land. If the rich want to build their manor on some good spot, the poor that live there will have to leave. But if a cancer treatment is found for the rich, it will not take away a cancer treatment for the poor, in fact, that's the opposite, as it is likely that a few years after, the poor will also get the rich treatment.