Abstract: Both free markets and government regulators tend to use willingness to pay (WTP) to measure the value of goods. The reason for use of WTP is that it is the best and the most administrable method for (1) capturing the relevant welfare effects and (2) respecting personal autonomy. At the same time, WTP might be infected by a lack of information and by behavioral biases. There are also philosophical objections to certain uses of WTP, pointing, among other things, to the problem of adaptive preferences and to turning certain goods into commodities.