I think you're wrong about this. 35 years ago was 1990. Nobody was selling vulnerabilities in 1990 at all. By 1995, I was belting out memory corruption RCEs (it was a lot easier then), and there was no market for them at all. And there has never been a market for web vulnerabilities like XSS.

Building reliable exploits is very difficult today, but the sums a reliable exploit on a mainstream mobile platform garner are also very high. Arguably, today is the best time to be doing that kind of work, if you have the talent.