I've stopped giving GameStop my business since an incident over a decade ago.
For you fellow old farts out there, this was around the time the PlayStation 2 was nearing its North American debut. At the time, the Dreamcast was still alive and going strong, and I'd gotten one close to launch and had a good handful of games for it, too. But that PS2...man, I was drooling over that.
Those graphics! DVD playback! Backwards compatibility! Plus my PS1 was close to failing, and I had way more games for that than I did for my Dreamcast. So I made the hard decision to trade in my Dreamcast towards the pre-purchase of a PS2. I packed up the console, all the proper cords, both of my controllers, my VMU and all of my games (still complete and in good shape, even with their manuals intact). I put all that in a box and took it down to GameStop.
There was a couple hundred dollars' worth of stuff in that box, and although I wasn't expecting to get the full value for any of it, I sure wasn't expecting the value rattled off to me by the GameStop employees. The guy takes the box from me, goes through it, checks the console for external damage, checks the surfaces of the discs, nods satisfactorily, then sets the box aside and turns to face me again.
"Twenty bucks."
"Wait...excuse me?"
"I can give you twenty bucks for this."
(indignant) "Twenty dollars for all THIS??"
"Well, yeah, that's what we pay for stuff in this shape."
"Six high-quality games, no sports games or crappy movie license games, the console with everything it originally came with, PLUS a VMU and an extra controller, and you're offering me twenty dollars?"
"Well, yeah! The trade-in value's gone up since last month!"
"......Never mind. I'm taking this home."
I picked up the box and walk away from the counter, checking the prices on the used copies of the games and console I'd just tried to trade in. For the exact same combination of items I was offering them, they were more than willing to charge around $300 to consumers.
That's only one story in my arsenal, but it's still the most relevant to me. I don't do business at GameStop anymore.