In 2010, the Cornell University Library adopted a new business model to broaden the funding base for arXiv.org. Although this community-based interim model has garnered strong support, it also generated a range of questions in regard to the sustainability of open access online resources with a global user base such as arXiv. Making a case for such systems requires more than reliance on common quantitative measures that indicate submission and usage, statistics. Based on a sociotechnical systems approach, this article proposes a set of principles with which to evaluate return on investment as we consider the sustainability of open access subject repositories.