Which is pretty much common sense, as is the notion that you should check the price online before you sell. So why does this work? Because people trust friends and acquaintances more than some stranger in a shop; if you're in a home, you feel more trusting. The parties often involve alcohol, which is not a good negotiating tool. As the poor labor market drags on, I expect that this sort of thing will only get more common.
This article available online at:
http://www.theatlantic.com/business/archive/2009/11/scam-of-the-day/30152/
