Seller brings a pin for sale, puts it on the floor for free play and his entrance fee is waived for contributing to the show.
Attendee pays $17 entrance fee and gets to play a buttload of pins for free. While there, he decides to buy a pin and then CHOOSES to pay an additional $25 to remove it from the show.
Both buyer and seller got to enjoy the show. Buyer has to pay an additional 25 dollar convenience fee if it is inconvenient for him to leave it on the floor.