Everyday, all of us spend money on things — things we need, and things we don’t. And in turn prices are put on those things. But where do those prices come from? How much has to do with supply and demand? And how much has to do with bigger forces at play? Finance writer Eduardo Porter has been researching these questions for years. His new book is called “The Price of Everything: Solving the Mystery of Why We Pay What We Do.” Porter joins us to talk about the nature of value in modern society, some of its mysteries and explanations.