Prison Architect, one of our top 30 indies to look forward to this year, has recently sold $1 million in pre-orders. $1,023,040 to be exact, totaling 30,466 copies sold according to the website. The game is only in its alpha stage, but pre-ordering a copy now gets you immediate access to the current build of the game.
You can pre-order the game now from the official website for $30, or you can chip in more for better rewards. Sort of like Kickstarter's tiered rewards, except this game is already going ahead and obviously doing quite well.