When I wasn't even involved in the internet yet, I had the opportunity to manage a YouTube channel in the fitness niche. I was just a kid; I remember still living with my parents.
At first, the guy didn't even pay me. Later, we agreed on the exorbitant amount of €200 per month for my work, which he often paid me late even. The deal was that basically he would pass me all the raw, unedited content, and I would take care of practically everything else.
When I took over that channel, it had about 4 or 5k followers, and when I disassociated myself from it, it had over 100k.
The thing is, even though I couldn't give specific numbers since that data didn't come to me, I know for a fact that this guy was making similar figures to those mentioned by lukmat, as his main source of income wasn't the "views"; in fact, we didn't even have adsense activated. He did remote workout and diet plans, had physical locations (gyms), and held seminars. We were also looking into launching our own line of supplements, I'm not sure if that last part ever materialized.
In the final period, conversations with him about his concern for earning those amounts without declaring them were becoming more frequent. Additionally, I know he acquired some properties.
There are many people in the shadows making unsuspected amounts considering the size of their audience, not everything is adsense or traditional monetization.