Context: It is well established in the literature that healthier diets cost more than unhealthy diets. Objective: The aim of this review was to examine the contribution of food prices and diet cost to socioeconomic inequalities in diet quality. Data Sources: A systematic literature search of the PubMed, Google Scholar, and Web of Science databases was performed. Study Selection: Publications linking food prices, dietary quality, and socioeconomic status were selected. Data Extraction: Where possible, review conclusions were illustrated using a French national database of commonly consumed foods and their mean retail prices. Data Synthesis: Foods of lower nutritional value and lower-quality diets generally cost less per calorie and tended to be selected by groups of lower socioeconomic status. A number of nutrient-dense foods were available at low cost but were not always palatable or culturally acceptable to the low-income consumer. Acceptable healthier diets were uniformly associated with higher costs. Food budgets in poverty were insufficient to ensure optimum diets. Conclusions: Socioeconomic disparities in diet quality may be explained by the higher cost of healthy diets. Identifying food patterns that are nutrient rich, affordable, and appealing should be a priority to fight social inequalities in nutrition and health.