>> So <$5 per month for someone in the developed world to keep using Instagram and stop being the product.

This is only true if everyone does it; Why would they stop advertising for a tiny market, especially if they can get both? Why decrease the value of the tracking on a smaller userbase? Sales conversion says you'd have to charge $50 or $500 a month and you'd have a much smaller base; does social media like this even work with a fraction of the people?