The amount of money a person was willing to forgo in order to give $75 to another person decreased as a hyperbolic function of the perceived social distance between them. Similar hyperbolic functions have previously been shown to describe both time and probability discounting.
Jones, Bryan A; Rachlin, Howard (2006). Social Discounting. Psychological Science 17(4) 283-286. doi: 10.1111/J.1467-9280.2006.01699.X. Retrieved from https://oaks.kent.edu/psycpubs/122