PMax asset groups not segmented by product margin or category
When a single PMax campaign contains all products with a single ROAS target, Google's algorithm allocates budget toward whatever converts most easily. That is usually lower-priced products, products purchased by repeat customers, and products with the most historical conversion data. High-margin hero SKUs that need new customer acquisition compete for budget against low-margin products converting existing customers. The campaign reports a blended ROAS that looks acceptable, but the margin-weighted return is significantly lower.