This paper examines the testing and the pricing of orphan drugs, e.g. drugs for patients suffering from rare diseases. Due to the small size of these populations, orphan molecules question established evidentiary practices, namely randomized controlled trials (RCT) and health technology assessments (HTA), driven by numbers and statistical reasoning. Drawing on the notions of “statactivism” (Bruno et al. 2014) and “evidence-based activism” (Rabeharisoa et al. 2014), this paper shows how stakeholders in the field of rare diseases come to test a variety of solutions, ranging from adapting RCT and HTA on the fringe, advocating for exceptional procedures, to recomposing RCT and HTA from within. These initiatives offer new insights into the pricing of orphan drugs as a testing device of who is accountable for the evaluation of these molecules, and of how rare diseases are made to count for society at large