Google does not reveal exactly how much revenue it generates from YouTube. The company lacks transparency. The company does not reveal how much it generates from each of its platforms. This makes it difficult for researchers to track down the revenue of the company.
According to Business Insider, "Credit Suisse then broke out YouTube's revenues alone, and predicts they might grow to $6 billion in 2015".
This information would only be accurately gained by a researcher setting out to measure earnings of a very large sample of video tubers. That sample would have to represent all countries, and a boy in his bedroom (there will be many such you tubers) as much as a corporate company in order to reach an accurate sample. to the best of my knowledge this hasn't been done.
Google information does show that earnings are neglible until you hit 1 million views. Yes. Their $18 per 1000 views (after advertiser's take) will be a weekly income for some, modifying the really high earners.