The article highlights the importance of metrics in measuring the success of online advertising campaigns. It emphasizes that advertising is about acquiring customers, not just generating leads. The author introduces three key metrics: Customer Lifetime Value (CLV), Cost Per Customer (CPC), and Profit Ratio. CLV represents the average value of a customer over their lifetime, while CPC measures the cost of acquiring each new customer. By analyzing these metrics, businesses can determine whether an advertising campaign is profitable or not, and make data-driven decisions to optimize their campaigns. The article uses a fictional example of a project management startup to illustrate how to calculate these metrics and apply them to real-world scenarios.