Cam and Mitchell are on their way to Costco for some diapers, but Mitchell is surprised that they purchase items at Costco. He questions when this started happening and Cam jokingly acts like he means to act of purchasing diapers. Cam implies that the new baby has caused an increase in their demand for diapers. It turns out that Mitchell really likes Costco!
See more: demand, elasticity, necessities, preferences, quantity demanded
Economics of Modern Family 