Actually, if I read things right over at Registration: WFC 2002 it's $150 for membership. And I don't know if they do "day memberships" for people to wander around, but I suspect they don't. It's deliberately set that high to keep World Fantasy small (membership is also limited -- either to 750 or to 1000), and, for the most part, professional -- there are more publishers, authors, editors, artists, reviewers and such at a World Fantasy Con than there are "fans" (although many of the authors are also fans), and the people who run the convention try and keep it that way. No costumes, either.
There are many other cons smaller, cheaper, larger, cheaper, in the Minneapolis area and around the world. But World Fantasy is indeed expensive, and very much what it is.