The typical setup
You hire three agencies. Nobody owns the blended number.
Each one optimizes its own channel and reports its own ROAS. Every report looks healthy on its own. No single party is looking at contribution margin across all three shelves, and when the channels disagree, you arbitrate.
The structural risk
The cost is not just the bloat from three separate retainers. It's also the additional margin leaking between them, even if every channel report comes back green.











