What is Customer Profitability?

Legal Definition
Customer profitability (CP) is the profit the firm makes from serving a customer or customer group over a specified period of time, specifically the difference between the revenues earned from and the costs associated with the customer relationship in a specified period. According to Philip Kotler,"a profitable customer is a person, household or a company that overtime, yields a revenue stream that exceeds by an acceptable amount the company's cost stream of attracting, selling and servicing the customer."

Calculating customer profit is an important step in understanding which customer relationships are better than others. Often, the firm will find that some customer relationships are unprofitable. The firm may be better off (more profitable) without these customers. At the other end, the firm will identify its most profitable customers and be in a position to take steps to ensure the continuation of these most profitable relationships. However, abandoning customers is a sensitive practice, and a business should always consider the public relations consequences of such actions.
-- Wikipedia