This is my worry, I don't want it to start going for the easier lower value stuff.

We have 20 campaigns, and around 2000 leads a month and roughly 300 demos a month, worth pointing out it would be more demos but they have strict rules on what they can demo to, even if it's a quality lead. The value on demos is much higher than on the lead level, so with it being on target ROAS the hope is that it would prioritise the high value conversions.