I don't see any reason why a company needs to pay any percent of their revenue instead of a flat fee. You pay a % of revenue when someone is your partner or an investor in your company. Apple is neither. In fact, they've shown to be the opposite of a trusted investor/partner as they've copied successful apps and integrated them into their own platform.
The App Store should be a fixed fee, something like $19/month, for your app to be on sale there.
On another note, regarding your first comments, in the late 90's Microsoft went through DOJ depositions and demands for breaking up simply because they bundled Internet Explorer with their operating system. It didn't charge Netscape money for access to Windows and IE wasn't generating any income. But the furor at the time was huge and the anti-MSFT attitude has prevailed to this day. Why not the same feelings for Apple who's made this far more extreme and far more anti-competitive.