Global supply networks in agriculture, manufacturing, and services are a defning feature of themodern world. The efciency and the distribution of surpluses across diferent parts of thesenetworks depend on the choices of intermediaries. This paper conducts price formation experimentswith human subjects located in large complex networks to develop a better understanding of theprinciples governing behavior. Our frst experimental fnding is that prices are larger and that tradeis signifcantly less efcient in small-world networks as compared to random networks. Our secondexperimental fnding is that location within a network is not an important determinant of pricing.An examination of the price dynamics suggests that traders on cheapest—and hence active—pathsraise prices while those of these paths lower them. We construct an agent-based model (ABM) thatembodies this rule of thumb. Simulations of this ABM yield macroscopic patterns consistent with the experimental fndings. Finally, we extrapolate the ABM on to signifcantly larger random and smallworld networks and fnd that network topology remains a key determinant of pricing and efciency.