The article compares different ways money works in economies. It looks at bargaining, price taking, and price posting. The researchers use a general matching technology to study how money affects trade and entry in each structure. They find that under bargaining, trade and entry are inefficient, and inflation causes welfare losses. Price taking solves some inefficiencies but not all, and inflation can actually help. Price posting is the best, with the Friedman rule leading to optimal outcomes, but inflation still causes some welfare losses.