Diminishing Marginal Utility Imagine that apples and oranges are $1 each. The curves now show the marginal utility per dollar of spending on apples and oranges. Suppose the consumer spends her entire budget of $10 on oranges. The 10th dollar of spending on oranges increases utility by 9. If the consumer spent one dollar less on oranges (−9 utils) and one dollar more on apples (+70 utils), the consumer’s total utility would increase by 61.