The term "economon" (i:'ka.nə.muhn; plural: economa) is introduced here to describe an economic unit composed of two participants engaged in mutually reinforcing operant behavior. Economa are basic building blocks of transactional behavior that aggregate in social networks called economies. In a drug-addiction economon, operant behavior by one participant (the "supplier") provides an addictive drug as a reinforcer to the second participant (a "Person with Substance Use Disorder; PwSUD"). Reciprocal operant behavior by the PwSUD usually provides money as a reinforcer to the supplier. After defining the features of the drug-addiction economon, this article discusses its implications for (1) prevalence and virulence of drug addiction, (2) opportunities for drug-addiction research in general, (3) the "brain-disease model of addiction" in particular, and (4) factors that mitigate harm or promote risk of drug addiction. The economon model is intended to provide a novel perspective on the uniquely human disorder of drug addiction.