Earlier quoted context omitted.
There are literal kids (teenagers) making 6 figures a month from their Youtube channels with absolute 0 production costs. The best example would be a guy called Pewdiepie[1], he makes gaming videos and does something like 5 million views per day (which is probably around $10k revenue assuming he has a good deal...). He isn't alone, there's quite a few others approaching his level of success. Something a lot of people…
There is also the fact that this is only ad revenue. I would wager that people with good marketing skills make much more from side gigs than from direct ad revenue.
Not to mention that several producers have multiple channels, where they use the success of a single channel to make their subsequent channels just as successful.