This isn't a "processing" fee. This is a new kind of fee. It's a "platform access" fee. Apple sees value in the fact that they've cultivated a mass of users who are more than willing to repeatedly spend small amounts of money on content. I don't think that point can be overstated. iOS users buy a ton of content, and anyone with content to push wants access to them.

Hence, the standard rules of supply and demand apply. If you control 100% of the supply, you are a monopoly, so the question will become one of defining the supply. Is it iOS users? Is it mobile device owners? Is it media consumers? Where the definition falls on that continuum will define the outcome of the investigation.

I'd be very surprised if the regulatory agencies defined the supply as iOS users, so I think Apple will get away with this. Not that it matters much. I believe Apple has crossed the critical tipping point where sustainability exists only in niches, and will ultimately push away so many content distributors that the actual creators (those with the room to sell at a 30% markdown) won't be able to fill in the gaps fast enough. There will be volumes of content available on other platforms, and the attractiveness of iOS devices (and platform) will diminish. This will have the effect of accelerating competing platforms' growth lead. At that point, Apple will either react to the market, or relegate themselves to a small portion of the market that they will happily turn a huge profit on.