I had a hard time price comparing graphics cards on Amazon, so I made this website:

http://www.gpugarden.com/

It pulls used and new prices from Amazon and shows them in a grid.  That way you can easily price compare, and see if there is a good deal on a card.

I can add different chipsets/products if people are interested.

Let me know what you think! 

http://www.gpugarden.com/images/screen.png

Update June 9, 2013
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Today's update will give you better insight into price fluctuations on cards.

* Killer feature.  Typical hash rates are listed, and that is used to calculate hash rate against cost.  You can easily see what the best value is for new and used cards now on Amazon.
http://www.gpugarden.com/images/typical.png

* The below image shows "Lowest Price Seen!" feature.  If an item reaches a new low, this message is displayed.
 http://www.gpugarden.com/images/lowest.png

* When prices change, they are tracked and a sparkline is shown with the last ten price changes.  You can mouse over the graph to get pricing details.
 http://www.gpugarden.com/images/sparkline.png

Update June 7, 2013
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* Added icon that indicates Amazon Prime availability
* Tracking price changes, for future update after gathering more data
* Added google+ and twitter buttons