Companies like Diesel don't work on advertising, in the same way, little porn webmasters do. They don't look at the TV ads and relate it to sales the next month. They're establishing a brand, style and trend.
Do you really think Calvin Klien itemise CPM on how many sales they make in stores after this went up on a billboard?
Of course not. Think of it in terms of have a free bar at a porn show.
Once Tubes are tapped into a market that doesn't care about CPM, like those with little money to spend. They can expand and expand. How much of that trickles down to the little guys is the question?
Because mainstream will take over Tube advertising, making the CPM unprofitable for the people who now rely on it.
The only balance is the return for submitters to Tubes in getting enough buyers from a clip to make it profitable.
Looking long term, imagine a day when enough money is raised by advertising to pay for content production, and not rely on membership sales. It's possible.