What is the best/worst you've done when selling at a swap meet?

I have been a Ford guy, a Mopar guy, a Chevy guy and back to Mopar. Wife's family was Chevy, so I got 1. Got a 69 Z28. started collecting Chevy stuff. had 5 DZ 302 Z motors. Traded 1 to a guy for 11 bb Chevy motors, oval and square port heads, alum intakes, etc. Took stuff to swap meet 1 year later and had to give it ALL away for 500.00. Best was at a local all makes swap in Belleville, Il. My buddy and I took all our extra Mopar stuff, about a truck pull and came home empty. we made about 500.00 a piece. That was a lot of money in the late 70"s.