Some people condemn price discrimination for the same reason as racist discrimination. Take senior discounts in which sellers charge people over sixty-five less money for the same good or service. Sellers do this, because seniors tend to have less money than non-seniors and offering them a discount is a way of getting them to buy the product. The seller would prefer to be even more discriminating and to charge every individual a different price based on the buyer's willingness to pay it. But the seller has no cost-effective way of determining each person’s demand price. So the most efficient method is for him to identify differences among groups of people and to discriminate on that basis. While identifying group differences is not as discriminating as the seller would like, it’s the best he can do.