Here is an interesting site.
Trying to find the price of a certain product? This is your solution! http://priceonomics.com/
“Priceonomics is building a smart, curated catalog of all the products ever made, as I wrote when I broke the news of the startup’s launch in December. It identifies an item, and then crawls the web looking for every price it’s being sold at second-hand. It then gives you a suggested price you should be willing to pay, plus an acceptable range and how the price has changed over time. It then links to eBay, Craigslist, and other places where you can buy the product.”- Josh Constine, Techcrunch