My first piece of advice to you would be to NOT BUY ANYTHING from that store. Mark-ups like that boggle the mind, to the point where one has to wonder how they stay in business. They must be the only store for miles.
Second, I assume this place accepts trade-ins? I'm curious as to how much they would pay someone for their copy of something like Conker's BFD. Either they'll straight-up insult you, or they will give you a very fair price (hence having to inflate theirs).