Costly actions in Bayesian Nash equilibria prevent truthful implementation of social choice functions.
The article discusses how to design a system where people make choices based on their own interests. It suggests that when people have to pay to make choices, their decisions should be based on making a profit rather than just personal satisfaction. The main finding is that if everyone has to pay to make choices, it's not always possible to create a system where everyone tells the truth and gets the best outcome.