Despite the pervasiveness of barter across societies, this mode of transaction has largely escaped the anthropologist's gaze. Drawing on data from fairs in the Argentinean Andes, this book addresses a local modality of barter known as cambio. Bringing out its embeddedness within religious celebrations, it argues that cambio is practiced as a sacrifice to catholic figures and local ancestors, thereby challenging a widespread view of barter as a non-monetary form of commodity exchange. This ethnography of Andean barter considers processes of value creation, both economic and subjective, to further our understanding of how social groups create themselves through economic exchanges.