Apple is dominating the high end mobile market, where profits and the most desired customers are. (People who pay for apps and spend money within apps)

http://techcrunch.com/2015/04/14/revenue-gap-between-ios-and...

The "free with contract" or sub $400 market is a cut throat race to the bottom between Samsung and Xiaomi. Apple chooses not to enter that race (despite several journalists claiming they NEED a cheap phone to survive).