I think it's similar to any other human achievement (e.g. athletics) or even something like fine wines or instruments. Highly accomplished violinists are already an incredibly small subset of the population, but what separates the best of the best from the others is usually at once incredibly minute, yet just out of reach for almost everyone. With a violinist, it might be superhuman reflexes and coordination (in the case of a Hilary Hahn) or it might be the ability to turn and sustain a phrase.

In the world of collectibles (wine, instruments, etc.) you see a super premium being paid at the very highest end, often many times what the "next best" fetches in terms of price, even if the difference is only .01%