While the topic of sustainable development has been extensively explored, there is a lack of quantitative assessment of economic sustainability in the scientific literature; moreover, the term is often interpreted with excessive attention to the environment but not socio-economic inequality. In addition, university cities are often considered the most sustainable, although the higher education system in the United States is often criticized for the inequality of access to it among different racial and other groups of the population. This paper adds to the debate about how the concepts of sustainability and economic development relate. Many researchers have noted that they come into conflict with each other because their ultimate goals are fundamentally different: a voluntary limitation of production and consumption in the interests of future generations and, conversely, the pursuit of well-being during our lives. We would like to explore the issue of economic sustainability, which, at first glance, may become a compromise between the two approaches outlined above. So, our study is devoted to exploring the ambiguous concept of economic sustainability, which can add some new knowledge to the understanding of how social, economic, and ecological factors relate to each other in the broader framework of sustainability. For this objective, we analyzed the economic sustainability of the town of Amherst, MA. The city’s top employer and core enterprise is the University of Massachusetts Amherst, with over 32,000 students and almost 2000 staff members. Based on a literature review, a hypothesis was put forward that a university city should have a high level of economic sustainability. To assess economic sustainability, the original methodology based on the US Cities Economic Sustainability Index (USCESI) was developed. It evaluates sustainability in three groups of parameters: society, economy, and ecology. The first group includes the level of racial diversity, the level of education of the population, and the access to medical services. The second group consists of the Gini coefficient by income level, the median cost of housing, and the unemployment rate. The environmental situation is assessed according to the Air Quality Index developed by the US Environmental Protection Agency. For comparison, the town of Braintree, MA, was chosen. As a result of the study, the USCESI was calculated for both locations. The analysis showed that both Amherst and Braintree have a high degree of economic sustainability. However, it was revealed that proximity to a significant economic center has a more powerful positive impact on economic sustainability than the location of a large university. In our paper, we proposed a new methodology for measuring economic sustainability with a special focus on inequality as a major problem in American society. The findings provide new knowledge about university cities and debunk the myth that they represent an exception to the general logic of urban development in the United States. A similar approach, with clarification of statistical indicators and a different emphasis, can be applied to other countries where inequality may be the main threat to economic sustainability, not in terms of access to higher education but in other areas.