The New York Times did a study on mobile data usage by 50 of the top news sites on the web. The results are pretty awful for a lot of outlets:
Ad blockers, which Apple first allowed on the iPhone in September, promise to conserve data and make websites load faster. But how much of your mobile data comes from advertising? We measured the mix of advertising and editorial on the mobile home pages of the top 50 news websites — including ours — and found that more than half of all data came from ads and other content filtered by ad blockers. Not all of the news websites were equal.
Advertising proponents like to say that these ads are keeping the content free for us to consume, but that's clearly not the case, with mobile data being sold for around $10/GB by the carriers. We're paying for it, one way or another.