There are two editions - a standard one and a Collector's Edition which contains a lot of bonus materials.
 Collector's Edition
Naturally, the Collector's Edition comes in a special box and includes a lot of extras:
The behind-the-scenes DVD will offer more than two hours worth of developer interviews and commentary on all aspects of the creation of The Burning Crusade, as well as trailers and cinematics from the game, and even footage of panel discussions from BlizzCon.
Two starter decks from the WoW: Trading Card Game are included with the Collector's Edition and three tournament-legal cards that go with them.
Players who purchase this edition can have an exclusive in-game pet - the netherwhelp.
Retail Price: 69.99�
 Standard Edition
Retail Price: 34.99� ($39.99)