Why would sellers go to a "place" where many others are also selling the same product? Wouldn't it better to go someplace off by yourself, so you can get the monopoly price? Well, the answer is that transactions"take place," meaning they require a context. Amazingly, it's better to go where all the other sellers are going, because of the problems of triangulation, transfer, and trust.  The Sears catalog was a "virtual" (paper) place, and Amazon is another "virtual" (online) place. But the answer to why we do that is "transaction costs." But then I go back in time to my own introduction to the notion of transaction costs, in a class taught by the remarkable economist Yoran Barzel. The puzzle is so simple that it seems dumb: why do we measure lettuce by the head, meat by the pound, and diamonds by the caret?Yoram Barzel, Measurement Cost and the Organization of Markets.The Journal of Law & Economics, Vol. 25, No. 1 (Apr., 1982), pp. 27-48https://www.jstor.org/stable/725223Plus, the TWEJ! And our first letter, as a homework assignment. If you have questions or comments, or want to suggest a future topic, email the show at taitc.email@gmail.com ! You can follow Mike Munger on Twitter at @mungowitz