It's supply and demand. If folk would only pay so much and there is plenty of stock, the price falls. If folk are willing to pay this much and the supply is fair the price rises.
And if there are few things left and there is demand, the price soars.
I don't know if they teach the old economics today called "Supply and demand."
OK guys I've been recently considering selling my xbone and building another gaming PC. My question here is, why is the used parts market so bad? I mean I can go online to newegg & buy a gtx 970 for $310 and get a free code for a new game or head on over to eBay & get the same card used for $280 W/ no code and it's been used for God knows how long and has been possibly used quite intensively. Same deal with CPU's I was looking for an i5 4690k. Neweggs price $239 ebays used price $200ish. Even used hard drives are only a couple bucks of (which is literally the last thing I'd want to buy used!) so out of curiousity why are the discounts on used items so negligible to new item prices?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic