Have you considered the lifetime value of your customer or client?
Carl Sewell of Sewell Cadillac has determined that each customer is worth $356,000.
Stew Leonard's Grocery has determined that each customer that comes in is worth $45,000.
It is imperative that you have a superior customer care team that provides an excellent customer experience. This way, you can strengthen the relationship of your business with its customers because every time they need assistance, you're always available as a business to address them with professional and courteous service with the goal of total customer satisfaction.
Then, you'll be on your way to calculating the lifetime value of each customer that you have.