All entrepreneurs, whether offline or on need to know this key number to run a profitable business. We online marketers have elaborate tracking for conversion rates, click through rates, etc, but we do not track the lifetime gross profit of a customr. Even a company just starting out should have some idea of this number, otherwise how do you determine the price of your product.

The first step as a new business, you should research industry data, ask others to find how long the average...