Google is introducing a performance-based cost adjustment feature for Demand Gen Target CPA (tCPA) campaigns on YouTube.
During the learning phase, if a campaign underperforms (fewer conversions than expected), Google may retroactively lower costs to keep your CPA closer to target.
The feature activates within five days of campaign launch and can remain active for up to three weeks, automatically adjusting spending in the background.
Read the full update here: About YouTube performance-based cost adjustment for Demand Gen Target CPA campaigns (Beta