|Mouse image from Wikipedia - creative commons licence.|
The researchers offered participants in their study (who seem to be students in Bonn) an opportunity to earn up to €20 by having a mouse killed - though as a minor detail the mouse was a surplus mouse and would be killed unless they chose to keep it alive. They found that only 46% of participants were willing to kill the mouse for €10 when it was entrusted to their care, but 72-76% were willing to kill the mouse for €10 when the transaction was subject to an auction market.
This is of course reminiscent of the famous dialogue between a Philosopher and a Socialite which I came across in Bob Townsend's classic book Up the Organisation (published in 1970 but now I'm pleased to see re-issued) As I recall it a Philosopher and Socialite meet at a party. He asks her if she'd sleep with him for $1M . She's being honest and says yes. "Now what about $10?" he asks. She's outraged: "What do you think I am, some kind of a ..." "We've already established that, now I'm trying to find out your price." ($1M in 1970 is $6M in today's money).
It's also interesting to see a paper in Science referencing Karl Marx.
I took great exception to Prospect describing Sandel and Graying as "two of the world's greatest thinkers." However Graying did a competent job of interviewing Sandel and the results are online here.