I see two problems with estimating price off craigslist. 1. List price is not the same as selling price 2. The averaging is being moved by "accessory items" i.

I see two problems with estimating price off craigslist. 1. List price is not the same as selling price 2. The averaging is being moved by "accessory items" i.e. http://priceonomics.com/computers/apple/macbook-air/ http://priceonomics.com/computers/apple/macbook-air/ shows a lot of things that aren't MacBook Airs in the low price bracket. Maybe tossing out anything that is a few SD away from the average would fix that.