Guy at the Dayton flea market swore sealed PS2 games were worthless, so I passed on a $3 copy of Katamari
This older dude with a card table full of sports games kept telling me nobody wants sealed stuff, it just sits there. So I skipped the bin he pointed at and grabbed a loose copy of Tekken Tag for $2 instead. Looked up that sealed Katamari that night, it goes for around $180 now, and I'm still kicking myself. Anyone else get burned by a vendor who clearly had no clue what they were talking about?