What's the use of medical advancement that can't help more than 10% of humanity?When the patent expires everybody benefits. Until then, it's available to everyone, but they must help pay for the drugs development. If nobody pays, the drug isn't developed, and nobody gets any benefit.
It's far more important that we move to a world in which all human beings have access to basic sanitation and healthcare than it is to spend billions of dollars attacking statistically rare diseases producing medicines that will help only a few rich people.
Would you die for that? You expect others to, no? That's kind of totalitarian. At the same time, this argument is fallacious in the sense that it assumes we should address no problem until the lowest level problem is solved for everyone. That's undesirable for a large number of obvious reasons I will not bother enumerating.
Do the "few rich people" that are helped not end up paying for the R&D of the treatment for everyone else in perpetuity?
In fact, I'd go one step further and argue that your statement is actually false in the long term. A world where all humans have access to good healthcare and education would actually be a world in which more people contribute to research and development of new drugs and one in which knowledge would advance faster.
That's a nice thought. Unfortunately, there is a huge advantage to not paying development costs, in that you can externalize them to others and reap the benefits, which is what many countries, including India and the UK, have chosen to do. In India it's ignoring the patent, in the UK it's setting a price ceiling, which effectively shifts the burden to the US since the profit maximizing strategy is still to sell the drug in the UK because marginal revenue exceeds marginal cost. If the US stops paying, the drug never gets produced, or gets produced much later because there is no private incentive to produce.