Are you excited enough about the StarCraft 2 beta to spend hundreds of dollars to get in?
To most people, spending $300 on an unfinished version of a game that will cost maybe $60 when it sees release is just outright lunacy, but to others, playing first is important enough that they're willing to splash out. Thankfully, for them at least, there are people online more than happy to take their money in exchange for the codes they seek.
At time of writing, there are 51 Ebay auctions for beta codes, with most seeming to have come from Blizzcon 08, which includes a World of Warcraft polar bear mount as an added bonuses. Prices range from just $26 on an auction with more than two days left to a $950 'Buy It Now' price, and the largest actual bid for a code is currently $305.
I appreciate that StarCraft 2 is a big deal, but personally, there's no game that I want to play so much that I'd be willing to pay five times the retail price just to get into the beta.