I am of the belief that Gamestop makes money off this ignorance on purpose. Not sure this is some real evil here with a plot to create a bargin bin of used game titles. However, Gamestop is run mostly by employees who are game fanatics but aren't able to do much else, with a number of customers who are clueless but buying stuff for hardcore videogame fanatics. And they create a cycle that is meant to lock yourself into there. Of course, with this, one can end up getting a range of experiences.
But employees do not equal the company. Unless the gamestop headquarters released a memo to all stores "Convince customers to sell their copies of Killzone 2" then it's not gamestop purposely attempting to profit from ignorance. And if they did release a memo like that it was take all of ten seconds for it to explode onto the intarwebs. Just because they do profit from ignorance doesn't mean that they are purposefully taking advantage of ignorance.
You can find me on facebook as Markus Van Rijn, if you friend me just mention you're from VGchartz and who you are here.