Where does cheap traffic come from?

So I sometimes can not understand how file sharing exists? I, of course, understand that the lion's share of their income is made up of users with paid accounts.

But how is it possible to provide the ability to download files up to 2 GB?

The cheapest traffic, where I even saw, is about 2 rubles per 1 GB. After all, if you count, it turns out that each file download will cost 4 rubles. But how do file sharing services on free accounts get this amount from each download?
')
After all, they at least do not work at a loss with the freebies.

Tell me, please, who knows where such cheap traffic comes from?