I think I understand the economics.
What I'm talking about is watching a Youtube video and having 5 five) ads plastered across the screens, or a news article and having another 5 (five) ads on the sides and bottoms, often covering content.
It's true, most, not all, but most of them have
Xs in the corner so you can kill them, but shortly another comes along.
I've spent a little less than $100 to kill them, with some luck. But it's a nuisance.