Often as a VC you are presented with a headline CPA figure and nothing more. This can look good on the surface but mask underlying issues. For example, take an early stage eCommerce business with an LTV of €30 and an overall CPA of €20. This looks like a solid business. Digging deeper, 50% of users are acquired through free channels (PR, SEO) and so the CPA for the remaining 50% (acquired through SEM) is €40. The free channels are often hard to scale up rapidly, so if the company wants to grow fast post-investment the obvious route is SEM. However, in this case customer acqusition through SEM is uneconomic (LTV of €30 is less than CPA of €40). As a VC you then start to worry about whether this business can grow fast in a rational way.