This paper tests the hypothesis that one important factor determining household availability of ready-to-consume products is their cost relative to the rest of the diet. National food expenditure surveys in the UK (2008) and Brazil (2008-09) were used. Purchased food quantities were converted into dietary energy (calories) and classified into three groups: (1) foods that are unprocessed or minimally processed; (2) processed culinary ingredients; and (3) ready-to-consume products, either processed or ultra-processed. The contribution of these groups to diets in each country was calculated as a percentage of total energy. Relative cost of ready-to-consume products in each country was calculated by dividing their cost by the cost of the rest of the diet (foods plus culinary ingredients). Linear regression analysis was used to test the association between the UK to Brazil ratios of the caloric share of different ready-to-consume products, and of the relative cost of these products. The caloric share of ready-to-consume products in the UK (63.4%) was well over double that of Brazil (27.7%), whereas their cost relative to the rest of the diet was 43% lower. The lower the relative cost of ready-to-consume products in the UK (compared with Brazil), the higher their relative consumption (R(2)=0.38, p<0.01).