ROAS (Return on Ad Spend) is a dangerous metric. It's incredibly easy to calculate, it makes the finance department happy, and it completely misses the point of sustainable brand building.
The Trap of Direct Response
When growth teams obsess over a 7-day, click-based ROAS, they inevitably funnel all their budget into bottom-of-funnel retargeting and branded search. Why? Because those channels capture high-intent users who are already at the checkout line. It looks fantastic on a daily dashboard, but it slowly starves the business of new audience acquisition.
You end up harvesting existing demand without ever planting new seeds. Eventually, your CAC skyrockets because you've exhausted your retargeting pool.
Measuring the Halo Effect
We need to measure indirect value. What happens when a user installs an app, never makes an in-app purchase, but refers three friends who become power users? Traditional MTA completely misses this network effect. As noted in the debate on MTA vs. MMM, we need broader frameworks to capture true impact.
Similarly, how do you measure the value of a viral organic TikTok that doesn't have a trackable UTM link? If you rely strictly on direct attribution, you will assign zero value to your most powerful marketing moments.
Building for the Long Term
Stop trying to tie every single dollar back to a specific user on day one. Incorporate macro-metrics like Customer Lifetime Value (LTV) to CAC ratio, Share of Voice (SOV), and brand lift studies. Marketing is an investment in future cash flows, not a day-trading exercise.