There is not something such as an average the cam girls do. In same site, model1 may do $500 in a day while model2 made $5 in a day. It is true that philipina and colombia girls usually do less than russians or romanians, but I seen philipina and colombians doing a lot too - maybe just due to one or two "boyfriends" who tip or private big.
It is true that many girls in chaturbate (but also in mfc if camscore lower than 700) may do $5 or less per hour, even if they're naked and chatty. But, they keep open at same time 3 or 4 sites, so multiply this for the open sites.
As example I checked now the models in tubecamgirl and I can see 3 or 4 of them in chaturbate and mfc at same time, this blonde is one:
http://www.tubecamgirl.com/norules/Kettis.html
http://en.chaturbate.com/kittysgrace/
(she is in mfc too but I don't know the nick - too many pages to look find her)
This is another one in many sites:
http://it.chaturbate.com/rosinna/
http://www.tubecamgirl.com/voyeur/Madalina.html
(she's in xcams and islive too)
So even if these girls are doing $5 per hour per site, that's still $15-$20 per hour total on all the sites open.