tl;dr
On businesses that can't afford 30%: Too bad, Apple wants to be the middleman
On price matching: Apple won't budge because their competitors (e.g. Amazon) insist on price matching
On the 30% slice itself: Apple is proposing that publishers (et al) will make more money at 70% than they'd make at 95% with someone else's business model
On (anti-)competitiveness: Apple is the only one which allows its competitors to have apps on its devices
Summary: iOS is a closed, controlled console system - more akin to Playstation or Xbox than to Mac OS X or Windows