AFAIK Youtube has deals with the labels so that they get a cut of advertising revenue for any music video. Also for anyone that uploads cover versions etc.
I wouldn't be surprised if that income is quite substantial.
Do you mean the total revenue isn't that substantial, or the cut of the income that flows downhill to respective people (like the artists, managers, etc) isn't?
Any artist royalty statement. (I manage a number of indie musicians). Same goes for Spotify. You are talking pence for hundred's of thousands of "views".
Probably costs more to account it to the artist than the actual royalty.
"Youtube partners will make in the range of $2.5 to $5 per 1000 video views The most popular stars will earn $5 per 1000 views. This can really add up if you have 1 million views per video. Nigahiga for example, will earn $5000 per video they put up. This range can vary depending on number of advertising clicks."
I wouldn't be surprised if that income is quite substantial.