[kukkeliskuu]

You are partly correct, although it really depends. My site is in Finnish, which makes Google AdSense the only really viable option, unless I want to spend lots of time finding affiliate marketing revenue. That pays approximately 1.3 euros per 1000 page views, and does not work well with mobile page views on my site. I get 2M page views on high season, now it is off-season and visit counts are lower. I really get only around 20 euros per day on ad revenue, which makes around 600 euros per month. 200 euros per month cost is not "trivial". I have some other revenue, but that is small as well. Header bidding companies are interested to work with you if you have 5M+ page views per month. On a longer term, I think there is potential, but sure, I have made the decision to make the site foremost a public service, and revenue is secondary.

[maeil]

That's an incredibly low CPM, especially since your visitors will almost solely be from Finland, right? It's not uncommon to earn ~$1k/month purely from ads on blogs with ~100k unique visitors/month. So your CPM seems >20 times less than that.

Do the better paying ad networks all reject you solely because of the language?

[kukkeliskuu]

I don't know why I get rejected. I don't even get replies to my requests. But I am guessing the language is important part of it.