Comment by dspillett

> I’d be surprised if it’s even $5 a month for many of them.

I doubt it is even that, or close, if you take any average reading.

> I don’t understand why some of these small blogs on niche topics even have ads.

I think in many cases they have the ads there just in case one day they randomly get mentioned in a high-profile place, get a pile of traffic, and that makes them an amount in ad revenue worth caring about. Of course, they probably underestimate the effect of such a glut of traffic, most likely their site will grind to a halt long before much ad revenue is totted up, and their “15 minutes” will be over before it is back up again.

In some cases it is simply that they've chosen to host somewhere “free” where they have little or no control over the ad content, and probably never see a penny of any revenue from it (the host takes that in exchange for the “free” services).