Market norms come into play any time money enters into the equation, sometimes counter-intuitively! Ariely gives the example of a group of lawyers who were approached by the AARP and asked whether they would provide legal services to needy retirees at a drastically discounted rate of $30/hour. The lawyers said no. From a market norms perspective, the exchange didn't make sense. Later the same lawyers were asked whether they would consider donating their time free of charge to needy retirees. The vast majority of the lawyers said yes. The difference is that, when no money changes hands, the exchange shifts from a poor-value market exchange to an altruistic and therefore high-value social exchange. It is a strange psychological quirk that 'once market norms enter our considerations, the social norms depart.'