How did a network of passionate academics with limited funding but big, comparative, education research ideas lead to an international assessment market? This paper explores the interests, capitals, and power dynamics embedded in the International Large-Scale Assessment (ILSA) market through a network ethnography to understand how the market emerged and what drives actors despite the lack of direct profit. This paper constructs an interdisciplinary framework combining sociological and business studies to analyse qualitative data on OECD and IEA ILSAs. Highlighting the role of social-cultural-economic capitals and business expanding processes, the paper describes an ILSA market that was and remains a non-competitive, desirable, and exclusive market that is impenetrable to outside actors. The paper concludes by asking how the ILSA market contributes to education as a common good.