CPI is useful. It tells you how much it cost to acquire each new user and helps you monitor campaign efficiency. But it only captures what happens at the beginning of the user journey.
The more important question is what happens after the install.
Do users open the app again? Do they make a first purchase? Do they continue transacting over time? Do they generate enough value to justify the investment?
This is where lifetime value becomes essential. LTV estimates the value a user generates throughout their relationship with an app. It connects acquisition performance with the business outcomes that matter after the campaign ends.
That also means a campaign with a higher CPI is not necessarily a worse investment. If it brings users who make more purchases, stay active for longer, or generate more revenue, those users may be more valuable overall than the ones acquired at a lower cost.
The key is to compare user cohorts over time, not just campaigns on the day they launch. Looking at retention, purchases, revenue per user, and reactivations can reveal differences that a dashboard focused only on installs and CPI may miss.
This does not mean leaving acquisition metrics behind. CPI, CAC, and ROAS still help answer important efficiency questions. The point is to use each metric for what it can actually tell you.
The right measurement starts with the decision the business needs to make. If the goal is to reduce acquisition costs, CPI matters. If the goal is profitable growth, you also need to understand the value those users generate after acquisition.
At Rocket Lab, we look beyond the initial result to understand which users contribute to long-term growth and where investment can create the greatest business value.
Lifetime value, or LTV, estimates how much value a user generates throughout their relationship with an app. Depending on the business model, this can include purchases, subscriptions, or other valuable actions.
They answer different questions. CPI measures the cost of acquiring a user, while LTV helps evaluate the value that user generates over time. Looking at both gives teams a more complete view of campaign performance.
Start by identifying which campaigns, audiences, and channels bring users who retain, purchase, and continue engaging with the app. Those insights can inform future targeting, budget allocation, and retention strategies.
Lorenzo Camillo, Senior Sales Manager EMEA at Rocket Lab. Rocket Lab is an App Growth Hub that integrates multiple solutions to help companies and their apps achieve their business goals through attraction, acquisition, and engagement strategies. Its solutions include Apple Ads, OEM advertising, programmatic media, and ad networks, supporting brands across the entire app lifecycle.