OPEC raised the price of crude oil in world markets. U.S. gasoline producers raised the price of gasoline. The U.S. government imposed a price ceiling on gasoline. Demand for gasoline increased. Maria decides to spend an additional hour working overtime rather than watching a video with her friends.
Rational people make decisions based on average cost.
People respond to incentives. Peoples face tradeoffs. The cost of something is what you give up to get it.