Food cost has a strong influence on food purchases and given that persons of low income often have more limited budgets, healthier foods may be overlooked in favour of more energy-dense lower-cost options. The aim of this study was to investigate whether modifications to the available household food budget led to changes in the healthfulness of food purchasing choices among women of low and high income. A quasi-experimental design was used which included a sample of 74 women (37 low-income women and 37 high-income women) who were selected on the basis of their household income and sent an itemised shopping list in order to calculate their typical weekly household shopping expenditure. The women were also asked to indicate those foods they would add to their list if they were given an additional 25% of their budget to spend on food and those foods they would remove if they were restricted by 25% of their budget. When asked what foods they would add with a larger household food budget, low-income women chose more foods from the 'healthier' categories whereas high-income women chose more foods from the less 'healthier' categories. However, making the budgets of low- and high-income women more 'equivalent' did not eradicate income differences in overall healthfulness of food purchasing choices. This study highlights the importance of cost when making food purchasing choices among low- and high-income groups. Public health strategies aimed at reducing income inequalities in diet might focus on promoting healthy diets that are low cost.