Apple take 30% of the selling price.
There is a a series of price tiers that you can opt to use.
You have to decide your price structure and if Apple does not have what you want, then you would need to find a publisher that does.
Apple supply free software to creat eBooks, they could having seen its potencial over the last 2 years or so... make a charge of $200 dollars and I an others would pay it! After all lots use inDesign which is really expensive.
Do your books sell in 1000's? If they are then $6 - before tax is paid - may seem OK.
Apple offer a tool to make books and a publishing system that puts your book in front of one of, if not THE largest potenticial audience, whether it suiuts you or you use it... is your choice.
http://support.apple.com/kb/HT5071
http://support.apple.com/kb/PH2808
http://www.apple.com/support/mac-apps/ibooksauthor/