Since Claxton et al. [1] first estimated a cost-effectiveness threshold for the National Institute for Health and Care Excellence (NICE) in England, several other research teams have replicated and adapted their methodology, and there has been a proliferation of estimates [2]. Subsequently, the University of York team has sought to reinforce their original estimate, and their latest contribution was recently published by Martin et al. in this journal [3]. The key quantitative output from these studies has been rebranded over the years, and in this commentary, we will embrace the latest moniker, the marginal cost per quality-adjusted life year (MCPQ).

Estimates of the MCPQ tell us something about how efficient the health service is in producing health outputs from health expenditures. But how should policymakers use them? In their recent article, Martin et al. [3] make several claims about how the MCPQ should be interpreted. Broadly, these claims relate to past performance assessments or future decision-making strategies. In this commentary, we use Martin et al.’s claims as a case study for exploring the validity of claims about the usefulness and policy relevance of MCPQ estimates. Though we focus on Martin et al.’s claims, our arguments are generalisable to other papers in this genre (see, for example, [4,5]).