Why blended beats platform ROAS
Every platform claims credit for the same sales, so summing their reported ROAS overstates reality. Blended ROAS sidesteps this: total revenue over total spend, no attribution required. MER is the same idea expressed as a ratio of revenue to marketing cost. It is the board-level truth that platform dashboards cannot flatter.
How to use it
Use blended ROAS or MER as the top-line health metric and platform ROAS only as a directional signal for optimization. When platform-reported ROAS rises but blended does not, the platforms are re-claiming existing sales, not creating new ones. It complements a single source of truth in the attribution stack.
Common questions
What is the difference between ROAS and MER?
Platform ROAS is per-channel attributed revenue over that channel's spend. MER (blended ROAS) is total revenue over total marketing spend, which avoids double-counting across channels.
What is a good MER?
It varies by margin and business model, and like ROAS it should be read against break-even. The value of MER is the trend and the fact that it cannot be gamed by attribution.