The only reason they aren't able to crush people is because of Android and Microsoft. If you look at how the App Store was run and the general way Apple did things before Android became dominant, it was pretty scary. There were stories almost every other day about Apple just arbitrarily banning apps that might have conceivably intruded upon their corporate interests.
But they could drop the prices on their devices and corner the market overnight. If Apple offered an iPhone 6 for $99 off contract and a $299 Macbook Air... not everyone would switch, but enough would that their competitors would have a hard time staying in business. And Apple could do it. Forgetting for a second that dumping is generally illegal, selling products at a loss in order to put competitors out of business isn't unheard of.
