We have decided to restrict bid optimizations for vCPM for two reasons:
The AdLabs bid optimizer is meant to grow sales within your target ACOS, but vCPM campaigns should be used to drive brand awareness through impressions or clicks and should not be evaluated by ACOS.
The "impression based sales attribution" for vCPM campaigns often leads to over-attribution of sales to these campaigns (cannibalizing organic sales). The inflated performance would likely lead to increasing bids & spend causing the account's Total ACOS to climb while the vCPM campaigns appear to have low ACOS.
For an example of Reason #2, see the inflated sales attribution for a group of vCPM campaigns:
The image shows vCPM campaigns with $22,667 in Sales at just 1.36% ACOS! 🤯 (For further context, this account averages ~30% ACOS overall)
I hope you can see why we avoid trying to calculate bids on vCPM cost type to hit the target ACOS.
We are willing to change our minds on this decision if we see strong demand for vCPM bid support. Let us know what you think!