Cost Per Acquisition (CPA)

Cost per acquisition (CPA) measures the total expense required to acquire one new customer. It is calculated by dividing total marketing and sales costs by the number of new customers gained during that period. CPA is a critical profitability metric — if it costs more to acquire a customer than that customer will ever spend, the business model is unsustainable.

Testimonials and social proof directly reduce CPA through multiple mechanisms. First, they increase conversion rates on existing traffic, meaning you extract more customers from the same ad spend. A landing page that converts at 5% instead of 3% effectively reduces CPA by 40% without changing a single ad. Second, video testimonials used in ad creatives often outperform stock imagery and generic copy, lowering cost per click through higher relevance scores.

Organic social proof — such as customer reviews, Wall of Love pages, and shared video testimonials — also reduces CPA by generating word-of-mouth traffic that costs nothing to acquire. Customers acquired through referrals and organic social proof tend to have lower CPA and higher lifetime value.

To optimize CPA, track it by channel and campaign. Identify which testimonials and social proof elements are present on your highest-converting paths, then replicate those patterns across underperforming channels. Over time, building a library of compelling video testimonials becomes a compounding asset that continuously lowers acquisition costs.