If you’re curious about just how the Diablo III Auction House is going to work, with all its in game gold and real life scratch, Blizzard has posted a detailed layout of how this is all going to come together. This is basically a getting started guide but I found some pretty handy info here.
Before you post your auction, you’ll see any fees that apply to your listing displayed in the center section of the Sell tab. These fees will only be charged if your auction successfully sells, and will automatically be deducted from the item’s final selling price.
There are a lot of fees involved.
So, basically, like PayPal and eBay. This all feels really dirty to me for some reason, but I suppose this is better than people going to eBay and hawking these fake swords and magical doo-dads and eBay getting the cut and not Blizzard.
Sidenote: If you spend real money on an item in Diablo III we can no longer be friends, by the way.