Blizzard announces a new Global Play functionality for Battle.net to allow Diablo III players to play on servers in different regions. They also announce a new Auction House Website for the action/RPG as home to the in-game auction functionality in the action/RPG sequel. This FAQ has all the details, including how the house rake will work:

In the gold-based auction house, a 15% transaction fee will be deducted from the final sale price of a successful auction.

In the real-money auction-house, for equipment such as weapons and armor, a fixed transaction fee will be deducted from the seller for each piece of equipment successfully sold. This fee is assessed only if the item is sold. For commodities such as crafting materials, gems, gold, and other “stackable” items, a 15% transaction fee will be deducted from the total sale price.
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Note that additional fees apply for players who choose to receive the proceeds of their successful auction via PayPal™ (in regions where this option is available). See the Functionality section of this FAQ for further details.