Define “high” here - I grew up collecting NES gear and games from the flea market as a teen (circa 2005) and it was perhaps $30 for a working NES console, most games were $5. Perhaps $10-20 for a Legend of Zelda or Super Mario Bros. Few times a year some empty-nesters would hold a yard sale at the flea market and one could snatch up their grown children’s abandoned childhood games, negotiate $20 for the whole box.

Nowadays you go to the flea market it’s a full-time reseller charging e-Bay influenced prices on all products. There’s no deal to be had. Feels like a death of an era sadly.

My personal theory on that is that you bought all your stuff at a specific time (like 2005 or prior) before the population of original 1980s NES-game-owners became old enough, established in their careers and started having enough disposable income to buy back all their childhood favorites in a new collection, driving up the market price per piece.