We seem to observe different patterns of exchange at different times and in different places. The first goal of this paper is to develop a model of money as a medium of exchange which allows multiple transaction patterns. A dynamic version of Shubik’s trading post economy is used, and it is shown that this economy allows a role for fiat money, and that fiat money can coexist with barter in exchange. There are multiple decentralized equilibria, and one of these resembles the equilibrium of a cash-in-advance economy—indeed, the model can be viewed as a generalization of the cash-in-advance framework. The second goal of the paper is to show that the present model can help explain why inflation seems far more disruptive and costly than what is implied by empirical studies on the cash-in-advance model. The argument for this is based on misestimations due to the unobservability of the patterns of exchange, which are variable in this model.