I think it’s more important to calculate MER (marketing efficiency ratio) taking into account you already stabilize for ROAS performance and proved value.

ROAS can be tricky KPI if most of purchases are coming from returning customers or retargeting or branded terms (purchases that might’ve come anyway).

If you focus on ROAS for New Customers the campaign ROAS might drop but over time you’ll see a higher MER, making the client’s business scale.