The content is not free to the end user and it's not given away for free by the publisher. The end user doesn't pay cash for it, but they do pay by becoming a target of numerous ads and a demographic metric for selling additional ads.
Let me answer your question with a question: Does Visa take a percentage of donations made to the Red Cross using a Visa credit card?
People would be a lot less upset if apple was charging a small processing fee, instead of a 30% cut.
If Readability wants make an iPhone app, and keep giving $7 for very $3 they make, they'll have to make their in-app purchase price $14.99. Also they can't charge less anywhere else.
IAP price = regular price / 0.7 then rounded up to the nearest integer (less a penny).
Let me answer your question with a question: Does Visa take a percentage of donations made to the Red Cross using a Visa credit card?