Everyone cares about clicks right, not impressions. What I'm saying is that a small business will need to spend more money to get the same amount of clicks as an affiliate.
Practically everyone that I know that runs CPM hard targets heavily. So the demos are typically <500k. The small business will need to spend more money saturating that demo than an affiliate. That's what I'm getting at.
In your example, if my CTR is high enough, then after 100k impressions I might say "Alright, I squeezed out the demo, I'm seeing my conversion rate dropping, time to change targets or try new ads". For a small business, those 100k impressions won't even scratch the surface for them in getting some sales, so they will keep paying for another 100k, and another, and so on.