The price decides everything

On the first day of college, the Dean addressed the students, pointing out some of the rules: "The female dormitory will be out-of-bounds for all male students, and the male dormitory to the female students. Anybody caught breaking this rule will be fined $20 the first time." He continued, "Anybody caught breaking this rule the second time will be fined $60. Being caught a third time will cost you a fine of $180. Are there any questions?" At this point, a male student in the crowd inquired: "How much for a season pass?"