Apple doesn't deal in the used iPhone market, so any lost sales won't impact Apple either way.
It's not the first year Apple is going up against cheaper android smartphones, and you are not the first person to claim that Apple needs to make cheaper iPhones either. For whatever reason, iPhones have proven to be fairly price-inelastic. There will be consumers who get tempted by a cheaper android smartphone which they feel is good enough, but by and large, the people who want an iPhone will still get one, whatever the price (within reasonable limits).
I am not going to pretend to be some expert in this subject, but cheap android handsets have existed since the beginning, and Apple has continued to prosper in the face of said competition. I don't know exactly what the reason is, but I think that as Apple realizes that growth of the iPhone market plateaus, they will actually start to charge more for their devices in order to maintain their margins, instead of going down the path of profitless market share many before them have fallen trap to.
Of course, consumers are not going to be paying extra for nothing. Apple is clearly making the Apple ecosystem more sticky, as well as positioning the iPhone as the hub of your life so as to make it seem as indispensable as possible. Whether Apple will succeed or not, we shall see.