Was it the last day of the show and/or near closing time? Long-distance dealers with heavy, bulky items (such as books) will often slash the price near show's end, so they don't have to pay to ship them back with them. It's cheaper for them if they sell at a loss, than if they don't sell at all and have to go back home with them taking up space and weight in the luggage.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis