This dissertation explores the interactional basis of markets by asking how supply and demand meet in practice. Economic sociology has focused on how social structures, not calculation by rational agents, affect market outcomes. Transaction appears as an aftereffect of structural forces, yet for buyers and sellers it is rarely a "done deal." Following an unexplored concept in Weber, I asked how market exchange results from parties interacting, negotiating, and often failing. Sellers' attempts to engineer interaction make this process visible. Despite electronic banking, financial firms invest in face-to-face encounters again. In post-socialist Hungary banks re-personalize to deepen consumers' loyalty and their engagement with finance.

In my ethnographic fieldwork, I observed ordinary banking encounters and interviewed bank representatives. Bringing ethnomethodology to markets, I analyzed how people and devices accomplish situations together. To show that interaction is a capability related to organizational investments, I compared two methods of personal selling: a typical bank branch offering full-range finance, and traditional field agents of a specialized bank, who seek prospective clients for a home loan. Both developed technologies of mass personalization —tailoring how they offer generic products on a large scale. At the branch the software Customer Relationship Management (CRM) provided clerks with detailed profiles and product offers for individual clients. Meanwhile, home loan agents performed a powerful visual demonstration of their plan's advantages for each client, and developed a flexible script to personalize for anyone.

This dissertation makes three contributions. First, it unpacks market exchange as the outcome of social and technical interaction processes. Second, it addresses the place of the social in markets. Sociologists asked how social relationships, culture, or institutions underlie the impersonal, rational, economic logic of markets. Studying interactions, the social-economic distinction disintegrates as actors seamlessly blend elements of one-shot deals with those of ongoing trusted relationships. Third, it explores how interactions produce the parties to the exchange. As they react to each other, people turn into consumers with needs, their counterparts into experts, and products into relevant and meaningful objects in personal life. To grow, organizations construct salespeople by controlling interaction, which depends on completing cycles of data accumulation.