At what point should hugely disproportionate healthcare be provided to select individuals at the expense of everyone else'e healthcare?

I have Sarcoidosis, a genetic condition that means my immune system literally attacks my own body. It's extremely rare. Should I demand that a hugely disproportionate amount of money be spent to cure me so that I can enjoy this theoretical immortality? Seems a bit selfish. That money could presumably be spent to benefit many more lives beyond my own.

This isn't pro-capatilism reasoning, it's just being realistic and reasonable.

EDIT: To clarify I'm not advocating that we don't invest money in treating Sarcoidosis (or other rare conditions); right now it's much more realistic and more likely to cause immediate benefit than immortality moonshots! However, down the track perhaps the best investment would instead be prevention in newborns. In which case I'll miss out. A shame for me, but if that happens to be the approach that's going to have the best net positive outcome for society, then go for it.

If scarcity was an actual issue, we could collectively decide what a fair distribution of that scarce resource would be. Few things beyond a lottery would be considered fair by most, but we can try.

However, we live under conditions of extreme supply for many things, including most factors that would inhibit healthcare. We rarely need to choose.