GameStop doesn't directly sell any used consoles with a hard drive. The hard drives are always sold separate. They do however sell refurbished consoles straight from Microsoft that include a hard drive, for only $50 more than a new Arcade. Considering that GameStop makes just as little on an MS refurb as they do on a new console, I doubt they would've actively tried to push it over an Arcade, unlike when selling a typical used console. It sounds like it was just a friendly recommendation since, honestly, most people end up with a hard drive eventually anyway.
Also, while it was silly that the employees assumed the customer was wrong when he pointed out that the Arcade comes with a 256mb memory card, it's not very surprising that they didn't know the exact space of the internal card in the 360. Minor details like that change fairly often, and the importance of such a distinction generally matters little, so it's not a change most will take note of. Microsoft doesn't even bother to make sure GameStop employees know, and they basically have to find out such information on there own.
Now I ask, how many people here knew that an Arcade 360 comes with a 256mb memory card vs a 128mb card right now off the top of their head? Then figure that as active forum posting gamers, you probably know more than the average GameStop employee.
The customer was overreacting.
