We demonstrate a novel means by which the egoistic, affective motivations of charitable givers can be leveraged to increase donations: limit donors’ options to a binary choice between giving nothing or giving a specified amount (i.e., set a price). We first provide evidence of inelasticity of demand for charitable giving (N=287): increasing the amount requested 5-fold led to only a 13.3% decrease in the probability of donation. In a meta-analysis of 9 online experiments (total N=2,522), limiting donors’ choice set to giving a fixed amount or giving nothing raises more money for charity. We replicate this effect in a well-powered, preregistered study (N=2,850) and in a large field experiment (N=24,030) using physical mailers run by a national non-profit organization. Finally, we shed light on mechanism in an online lab experiment (N=2,027): the effect is moderated by individual differences in empathy, an affective capacity well-documented as a scope-insensitive motivator of giving.