I of course have no sources to back this up (how would one even get such data?) but I suspect billionaires have better things to do than go e-slumming with those of us with fewer than 30 cars.
Billionaires? Perhaps. But aren't most of us on here taking a quick break from our Silicon Valley-like software engineering jobs that put us in or near the highest income 1% of the United States, and firmly within the highest income 1% of the world? I'm sure any significant medical advance that is remotely scalable will be available to most of us if our competitiveness and survival depends on it.