How much does it cost to trade an iPhone 4 in for an iPhone 5 in the Apple Store?

I read it's possible to trade in your iPhone 4 plus some extra money for an iPhone 5 in an Apple Store. Does anyone know how much that would cost me with an iPhone 4 that only has some scratches on the back?

I didn't think about this. Sell it on ebay.

Check the estimate on Apple's site:
http://www.apple.com/...recycling/