In a post on the official Battle.net blog, Blizzard has announced that it will be introducing PayPal as the official payment partner for the Diablo III auction house, allowing users to purchase items in the in-game auction house using real-world currency. Blizzard recently announced that Diablo III would feature a separate auction house in which players would be able to sell their in-game items, gold and characters for real-world currency.
Though no further details were provided with respect to the integration of the payment service into other Battle.net titles, Blizzard did indicate that the service will soon be made available in several regions, and that it will be available as a payment method when purchasing digital products and services through Battle.net.
So beyond Blizzard taking some money for hosting fees, Paypal will take away some of your profit. Well it is probably the best service for auctions instead of having to deal with individual bank accounts and such.