That's my thinking too. It's not like a stupid PSP case. There are plenty of rare media items out there that fetch a pretty penny. For all you know, this was one of them.
However, I could see if you had a pattern of trading in stuff that was spectacularly overpriced (like the PSP case) then they might be like "this guy should be banned from trading."
my 2 cents.
i hardly ever trade in anything. This is probably my 3rd item I am trading in after pokemon black and fifa 11. I was actually planning on just selling this item instead of trading it in. I just saw that amazon was offering a pretty good gift card.