Let's just remind ourselves
that if you write a book for a traditional publisher, they will typically keep at least *85% of their net income.*
That's for books that sell reasonably well.
If you're a midlist fiction author, you typically get to keep just 7% of the net income.
Oh - and if you have an agent, the agent will keep between 10% and 20% of any payment the publisher makes to you.
Some agent contracts stipulate that you must pay them 10-20% of *any* work you do, from any source, whether or not they made it happen for you.
And the really evil ones expect you to keep paying them that 10-20% even after they're no longer working for you.
So that's how author-friendly trad pub is.
Now - if you're lucky, existing publishers will pay you an advance. It might be a few thousand for first time novel, although it's usually a lot less in the UK.
If you have a name and a platform (as it's called - i.e. you have some kind of relevant professional or media profile) advances can range from 10k to 100k. The real heavy hitters get seven figures. (But there aren't many of those.)
So - d'ya feel lucky?
With Apple you can write a book and keep 70% of the income.
With trad publishing you can write a book and make something less than minimum wage on an hourly rate basis.
Since publishers are no longer doing PR for non-famous authors, the Apple deal really isn't so bad - especially given that it's a new market, it's going to get bigger, and now is the time to make yourself a new niche.
You'll probably be wasting your time, especially if you don't know how to do the PR thing.
But some people will do okay. A smaller number will do more than okay. And a handful of people will do very well indeed from this.