A college student helps her roommate solve a unsellable stock crisis, only to be reviled overnight by the whole school as a black-hearted merchant. It was clearly a kind help, yet she was bitten back; behind the seemingly exorbitant business hides unknown heartbreak. When kindness turns into hatred, and goodwill meets greed, a contest over human nature and bottom lines officially begins. Seeing through the saying "a grain of rice wins gratitude, a measure of rice engenders enmity," Chen Min fiercely fights back. She cuts off relief to Lin Na's village, turning instead to establish a long-term trust pact with neighboring villages that truly understand gratitude. In this contest over "price differences," Chen Min deeply realizes that in this profit-driven business world, trust is the most expensive cost.