* 0.25% of 100B is 250M, not 10M.
* 2.5% of 100B is 2.5B.
OP's math, if you believe the assumptions, was right. Of course, the value of money goes down over time, since there's less time to spend it. I would rather have 10M at age 25 than 10B at age 80. One of the downsides of startups is you need to go through a few before you get to a successful exit, and as you point out, unicorn exits take a decade. 250 startups to wealth would mean you'd be wealthy long after you were dead. I'm not sure it's 250 startups, but it's also usually not 1.
OP was wrong about Facebook having a hard time beating 1M per year. I know plenty of people at FAANG above that. It's competitive but not impossible.
As for me, I'm making a modest salary (less than you make, most likely) at a job where I'm having the time of my life. I do impactful, meaningful, interesting things with all of my life. It's hard to beat that. Money is a means to an end, and if you're already there, it's not rational to optimize for wealth.
The only downside is possibility of loss of job, but if my job had the equivalent of tenure (e.g. I could keep doing this for the rest of my life), I wouldn't worry about money at all. But money has risks too.