So basically you would distribute the same way as in PC. You buy the install files in physical/digital form and install it. Then enter cd-key or something.
And of course somebody would come and make some kind of store to make the purchasing easier just like on PC. (for example Steam)
And yeah. Its ridiculous when Apple/Google take shares of the profits, comparing to what UE4 for example takes.
That's how you used to buy apps for phones. And you know what? Not many people bothered; it was a pain in the ass.
And heck, you can still do that on PCs, but most people go through Steam—because it's a much better buying experience.
Apple gives you a market place to provide marketing, handles the "do I trust them" problem, makes the pain to pay nearly non-existent (another CC form?), and handles the installation process for you. Ditto for most other platforms.
The platforms are more acting like Publishers than frameworks now, so directly comparing these prices is a bit hard.
"Valve captures 75 percent of the global market for digital PC games through its Steam store, researcher IHS Screen Digest has estimated."
http://www.bloomberg.com/news/2013-11-04/valve-lines-up-cons...
And also:
"Publishers earn a gross margin of around 70% on Steam, compared with 30% via retail stores."
http://www.forbes.com/forbes/2011/0228/technology-gabe-newel...
Unreal / Cryengine = 5% (Negative responses of high cost) But they actually provide the tools and are makers
Apple/Google = 30% for providing an app that lets you support their OS (What's an OS without Apps)