The only things you need to pay for is your internet connection (cable/dsl, dial-up, ect.) and a game card using either a store bought game card or using a Credit Card (kinda like an auto game card).
WoW In Progress -
Kuni - 60 - Hunter - Troll - Icecrown
Velbix - 45 - Shaman - Troll - Icecrown
Misuzu - 30 - Druid - Tauren - Icecrown