GameStop has been bartering with trade-ins for decades, and its program allows you to even swap your retro consoles for in-store credit. That's how it keeps itself stocked with old systems on its website that normally cost a chunk above second-hand listings, but whenever you see an in-store sign prompting you to "trade in gaming history", I need you to stop.
I should note that I live in Scotland, so my retro console collection is out of GameStop's reach. However, Bluesky User GWIZ shares a photo of in-store signage tempting players to trade in valuable systems and games, and even the wording of the pitch should be a red flag.