MineCraft has sold over 50 million copies at $7 (pocket edition) to $27 (PC edition) each, plus merchandise. Even after expenses, I'm pretty sure Notch's personal cut is in the nine-figure range. Easily enough to be independent for the rest of his life.

(I'm with you on "sell out at $2 million" in general, though. For the area I want to live in, which I coincidentally already live in, that'll last a lifetime.)