Energy-dense foods, some of which are high in refined grains, added sugars, and added fats, provide dietary energy at a far lower cost than do lean meats, fish, fresh vegetables, and fruit. Food costs may be one barrier to the adoption of healthier diets, especially by low-income households. Dietary guidelines, based on a pyramid of relatively costly foods, may not be the best approach to population-based interventions in public health. There is a need for more studies on the relationship between socioeconomic factors, diet quality, and diet costs.