ah, a useful thing to know about the Worldcon (if not for this year, then for the future) is that many people purchase membership far far in advance, when it's cheaper, and then closer to the actual date some subset of these people discover they cannot go and want to sell their memberships. Membership are easily transferred, and in fact you can often pick up a membership at a rate cheaper than whatever the current price might be. This is a useful reason for following the worldcon's LJ page, because offers to sell memberships pop up there quite regularly (and you could also post a note that you wanted to buy one).