My wife and I have a small life style business, selling a physical product. We make a nice daily profit using Meta ads. X dollars go in, X*A dollars come out, A > 1.0. When not running ads, it's just tumbleweeds.
I also have a digital daily browser puzzle. I've grown the user base quite a bit by running one simple ad on Reddit with amazingly good metrics.
In the past I worked for F2P mobile game companies. Their business is based on running successful internet ad campaigns.