http://www.forbes.com/sites/forbestechcouncil/2019/12/20/customer-lifetime-value-and-the-subscription-economy/?sh=6e4529556402

In our digital world, subscription services are more complicated. Specifically, a business’s costs, benefits and value of subscriptions are more complex. It’s no longer as simple as multiplying the cost of the subscription by the number of months and subtracting the costs associated with acquiring the customer and publishing and delivering the magazine.