Metrics
MER
Total revenue divided by total marketing spend, including non-advertising costs like email platform fees, SEO tools, creative production, and agency retainers. Provides a holistic view of marketing ROI that ROAS misses. Sometimes called the 'Bezos metric' because it reflects the true cost of customer acquisition across all channels. A declining MER with stable ROAS suggests rising non-ad costs are eating into overall marketing efficiency.
Why it matters
It is the whole-business efficiency number and cannot be inflated by attribution, because its denominator is all marketing spend and its numerator is all revenue.
In practice
Track it as the number the business is steered on and platform ROAS as diagnostics beneath it. If MER is flat while every channel improves, the channels are trading credit.
Related terms