Low margin products make paid search expensive because there is little room between what you earn and what you spend to get a customer. Marketers usually focus on getting the cost per click as low as possible by improving quality scores, writing more relevant ads, and targeting only the most specific keywords. Some also look at lifetime customer value instead of just the first sale, meaning they accept a small loss on the first purchase knowing the customer will buy again. Is lifetime value something you factor into your paid search planning?