In this post on the Freakonomics blog, the writer takes a look at how much her friend values their friendship based on Radiohead tickets. The band is performing in New York, which will be their first concert in the U.S. in about three years, and tickets were sold out in a matter of minutes. Her friend was one of those fortunate enough to buy a ticket (2 to be exact) and asked her if she would like to go. The author quickly looked at Craigslist to see what some people were willing to pay for these tickets ($400 to $1000 seems to be the average at this point) and then asked her friend what price they would be willing to sell her ticket for. It appears she has a good friend as they stated they would not sell the ticket now that it has been given to her (for face value) but said that if someone was willing to pay $2000, they would consider selling their ticket. Regardless, given the fact that they would not sell the ticket for $1000 (which many tickets are selling for) that means that the value of the friendship is greater than $900 (when you subtract the face value). Clearly this person is both a good friend and a big fan of Radiohead!

Source: Freakonomics blog