If you live in a VLCOL country, and have access to free tooling (via various means) you only need a very small return to make it entirely worth your while.

>Is it really worth the ad revenue to trick a few people looking into a few niche topics?

Maybe it's problem space exploration via pollution? Said creators of pollution (bullshit asymmetry theory in practice) have very little cost in creating said pollution and there is the possibility of a payback larger than that cost.