If in case the channels are doing really well then only will revenue flow in.. couple of years ago when I had the same idea it was approx 5 paise per view. So to generate Rs 500 per day.. you need at least 10,000 views everyday.
But once you surpass that limit, then as you said its free money.
Ha ha ...
Yaa, the channel should produce enough hits/views in order to produce substantial revenue. Also, the main point is that Views & Ad Impressions both are different. All views do not contain ads (i.e. impression). I always follow this data below (I found it somewhere over internet):-
YouTube's CPM is reported to be on average 7.6$, that means you get paid 7.6$ for each 1,000 views. Let's do the math in case and calculate the average scenario of 1$ CPM:
1,000 views 1.0$
10,000 views 10.0$
100,000 views 100.0$
1,000,000 views 1000.0$
10,000,000 views 10,000.0$
100,000,000 views 100,000.0$
1,000,000,000 views 1,000,000.0$
Let's do the math in case you're lucky and you got a 7.0$ CPM:
1,000 views 7.0$
10,000 views 70.0$
100,000 views 700.0$
1,000,000 views 7000.0$
10,000,000 views 70,000.0$
100,000,000 views 700,000.0$
1,000,000,000 views 7,000,000.0$
Also, if truth be told. The advertising revenue rates are different from country to country (which I feel is highly discriminating). Ad rates are higher in US, Australia and most of advanced Europe. In India, ad rates are extremely low. Hence, I always send request mails and do self promotion through mass mailing by targetting mail IDs of western countries only. Because as soon as they click on my videos, I shall get good revenue.