买贱卖贵

Explanation: Means to buy low and sell high 　　Usage: Joint type; as predicate, object; refers to the behavior of commercial profit 　　Source: Han Zhang Heng "Xijing fu": "Seoul is the family of one hundred merchants, traders Pi couple." Three Kingdoms Wu Xue Comprehensive Note: "Pi trafficking, buy cheap expensive, self-benefit." Thesaurus:  Convergence expensive cheap, Low progress overtop, Buy low and sell, Cheap grabbing your hair