I called CostCo about that very question and they were obnoxious about it over the phone. The guy said something like "Well, yes that would make sense that you'd have to be a member to buy something, now wouldn't it?"
I wanted to get into a whole conversation with him about how, actually, it does not make any sense that you'd have to be a member of an elite wholesale grocery store in order to buy a book, but instead I decided to spend that time finding a friend with a CostCo card. I'll borrow his card the day of the event and get in that way.
born this woway