The pre-paid alpha model seems to be working well for many indie game creators. Using it allows developers to create games while also getting paid, instead of waiting until it is finished and on sale. Introversion Software has become the latest success story, scoring them $8 million through alpha sales of the game alone.

Prison Architect has been on sale since September 26, 2012. In a press release, Introversion stated that since then the game has gone on to sell 250,000 copies, netting them that tasty $8,000,000. 

The game is still in alpha after a year, but is given regular updates to add to your digital dungeon. Prison Architect is available through Steam, with other various packages purchasable through the official site if you want to donate more.

What do you think? Do you think that purchasable alphas are a good way for indies to make money and fund development? Let us know in the comments.