There are two differentiators with iPhones and android devices. Price. The iPhone 5 costs a lot of money and yet android is significantly less and therefore more people will buy one based on price.

But what if the iPhone 6 went free. Apple could adopt the Google or Amazon model and make money from the software sales. Would this kill off android?

I doubt will we ever know, since I cannot see Apple moving along this business model. Not unless water freezes in hell first.