if you want the lich king you have to by all the older ones.
thats what one of my friends had to do, so you are looking at about 170$
to play the lich king...
if you don't have the other to games.
world of warcraft(50$)
WoW:burning crusade(50$)
WoW:the lich king(50$)
game card to activate account(about 20-30$)
i hate blizzard...
they rip you off at every thing they can...