Given a choice between making $400k a year (minus operating and maintenance expenses, which we have no idea of) and potentially making billions off an invention, which would you choose?
But as GP pointed out, it wouldn't be $400K a year. It would be $400K in year 1, followed by more or less exponential growth, even if he was just left alone to get on with it.
In actual fact, if it worked, someone would notice after a pretty short amount of time, and buy him up.
What's NOT going to happen is that someone reads one review saying it appears to work (but with no explanation how) and gives him forty seven squazillion dollars up front.