You're forgetting that the largest content companies are also the largest advertsising companies. For example, Google spends billions every quarter advertising. This is also why they maintained a $1Bil partnership with AOL believe it or not. Yahoo, Microsoft/Bing and the list goes on. All of their ad spending is part of what they consider TAC or Traffic Acquisition Costs.

Yes, I agree - it is an ouroboros (or whatever you call that snake eating its own tail). Ad tech has a byzantine complexity that is as complex on the business side as it is on the tech side: http://www.lumapartners.com/resource-center/lumascapes-2/

Google?

In 2014, Google's ad revenue amounted to almost 59.06 billion US dollars. That year, advertising accounted for 89.5 percent of the online company's total revenues.

http://www.statista.com/statistics/266249/advertising-revenu...