Development on this project has started in 2013 and scc shows "Estimated Cost to Develop (organic)" as $1.2M so for whatever that's worth it could be said to check those "5-7 years" and the "millions of dollars" boxes.
If you take into account the fact that Richard Hipp is not a billionaire whilst his software is used in almost all devices on (and not-on) the planet, his stuff is used by countless of megacorporations, etc, etc, then by my calculations: not nearly enough.
His paycheck alone should be tens of millions of dollars.
He should be making so much money that if he'd drop a 100 dollar bill it wouldn't be worth his time to pick it up.
Keep in mind that this project isn’t creating a new SQL database from scratch. It’s literally ingesting SQLite’s C source code and spitting out Go. cznic’s done an absolutely incredible amount of work here. It’s not ready for prod yet, but it works and passes all of SQLite’s tests.