The article says publishers keep 100% if the publishers sell the ads, or publishers keep 70% if the publishers use Facebook's ad engine.
Facebook's ad engine is the closest one to the Facebook social graph. Facebook's argument may be valid that ads on the articles served by Facebook will convert better.
That 30% might be made up by not paying a 3rd-party ad engine's commissions, plus the increased effectiveness of Facebook's ads.
> but why in the world would publishers give up 30% of their revenue
For a better experience for the user that will plausibly lead to better "click-through" rates?
I often don't click on articles on Facebook because I can't be bothered to wait 15-20 seconds for the page to load and stop re-flowing itself, then dismiss the "we use cookies" and the "subscribe to our newsletter" pop-over.
I read about this earlier today on /r/contentstrategist and they were saying that videos posted directly to Facebook get far, far more "plays" than if they are posted as links to YouTube. This is thanks to Facebook's AutoPlay for native videos, and whether people actually watch the videos more... Is not really interesting because plays/impressions is the metric by which a boss measures the marketing teams work, or how clients are billed.
So, this works because Facebook makes native content more prominent than linked content, which is filtered out.
> Ads can appear inside Instant Articles, with publishers keeping 100% of revenue if they sell them, and Facebook keeps its standard 30% if it sells the ads, as the Wall Street Journal previously reported.