$3.7 million sounds like a lot of money, but he could have earned more than that over 7 years if he just took a mid-level job at a FAMANG company. EDIT: saw that the founder lives in Birmingham, Alabama. So yes, $3.7 million IS a lot of money.
It averages out to $420k/yr. There's this sentiment on HN that "all you have to do" is get a job at a big tech company and you'll make a million dollars a year. It's idiotic, and not true. Yes, there are people who make $500k+ writing code in a cubicle for 40 hours a week. They are the vast, vast, vast minority compared to the people a) making $100-200k doing the same thing; b) making that $500k+ doing everything but…
There was a little bit of “pick the rocket ship” gamble - I had an Uber offer that probably would have been ended more like $250k/year, but it’s not unreasonable to get half a mill joining a late stage pre-IPO startup, and base salary is high enough you do it with little risk.
Hell, I know some mid-level post-IPO folks at Square making $700k due to it 10xing in share price.