Ashlee Vance, writing for Bloomberg on Apple's dominance of smartphone market:
Apple’s utter dominance of the money-making end of the industry stems from its business model and unique brand. Since stumbling in 2013 with the slightly down-market iPhone 5C, the company has redoubled its focus on an annual, highly desired flagship phone at a high price, turning its back on cheaper models for the masses. With the iPhone as its main profit center, the world’s biggest company has been able to invest in developing its own speedy, power-efficient chips and sturdy, lightweight materials, as well as continuing to refine its software.
My take on 5C - It think apple did this knowing the phone won't be a hit and since it won't hurt their business; they did a plastic cheap phone just to prove that people prefer a well built, nice looking phone made out of aluminum.