Consider a case of possible price discrimination - lunch specials at restaurants. some restaurants may offer a soup and salad for $5 during lunch hours and offer the same dish for $8 during dinner hours. let's suppose that the soup and salad is the cheapest dinner option, and that the restaurant, while usually only half-full during lunch hours, is often full enough during dinner hours that people end up choosing to eat elsewhere because of the wait. in what way might this difference in prices not be price discrimination? people that come in and order the soup and salad for dinner might cause customers who would have ordered a more expensive meal to instead eat elsewhere because of the wait. as such, the marginal costs of the two meals to the restaurant are different, and thus this isn't necessarily price discrimination. the restaurant does not have its servers trying to identify the elasticity of the individual demand curves of its customers and then charging different prices, and so this is not price discrimination. since different customers pay different prices for an otherwise identical meal, this must be price discrimination. people might be willing to pay more for soup and salad during dinner hours, and so the restaurants are not price discriminating since they are simply charging a higher price to people that are willing to pay the higher price. people often pay more for dinner than they do for lunch. if the price of a soup and salad during lunch relative to the average lunch price is the same as the price of a soup and salad during dinner relative to the average dinner price, then the restaurant is not price discriminating since the relative prices are equal.