The two main ways MMORPGs make money is through a subscription model, paying $5 - $15 a month to play, or through microtransactions, certain in-game items are purchasable with real world currency. Champions Online implemented both, a monthly fee, and the option to purchase costume pieces for money.
World of Warcraft, famously subscription based, is now entering the world of microtransactions. There were already paid services available, such as changing a character's server, name, look, gender, race, and faction.
It was previously reported that the Pandaren would be introduced into WoW as a non-combat pet. Blizzard announced that the pet is obtainable by purchasing it through Blizzard's online pet store. Half of the proceeds from purchasing the Pandaren will go to the Make A Wish Foundation, which Blizzard has worked with before.
Besides the Pandaren, there is also Lil' K.T., a miniature, or baby, version of the Naxx boss Kel'Thuzad. No proceeds from the purchase of Lil' K.T. go to charity, only from the Pandaren (those Scourge never do anything for charity).
Each pet costs $10.00. Once purchased, every character on the account, and every future character made on the account, will receive the pet. The pet cannot be shared with different accounts, and the pet will not follow a character transferred to another account.
This is probably just the start of the World of Micro-transactions. The other non-combat related, favorite collector's items are mounts, which are sure to follow soon, though no announcement has been made yet.