Explain how price differentials may be justified so that the Robinson-Patman Act is not violated

Price discrimination is forbidden only where such discrimination may substantially lessen competition or tend to create a monopoly. A plaintiff in a Robinson-Patman primary-line injury case must either show that the defendant, with the intent to harm competition, has engaged in predatory pricing or present a detailed market analysis that shows the price discrimination actually harmed competition. To justify price differentials to different customers, a seller may use cost justification or, alternatively, may show that its prices were lowered in a good faith attempt to meet competition. A seller may beat its competitor's price if the seller does not know the competitor's price, cannot reasonably determine the competitor's price, and acts reasonably in setting its own price.