Elaine's birth control sponge has been pulled off the market, and she's carefully hoarding her stash. So is the man she's dating "spongeworthy?" If she uses a sponge for him, she won't have it if a better opportunity comes along.
Elaine is in the bathroom, and finds her stall out of toilet paper. She asks the woman in the next stall if she can spare a square, but the woman says no. The woman turns out to be Jerry's date, and eventually he defends her by likening the scarce toilet paper to water in the desert: "You wouldn't ask a dying man in the desert for his canteen, would you?"
Kramer and Newman try to sell used records to a dealer who is buying them. He offers what they believe to be an insulting offer. This shows that value is determined by both scarcity and desire; without demand, even a rare commodity has no value.