And it has been estimated -- no idea how reliable those figures are --- that iphone 5 accounts for only 50% of new iphone sales. That means half of phone sales are older models 4 and 4S.
And let us not forget that US prices are distorted. Endusers pay the same $200-300 with a contract for the iphone they do for other high-end phones. But the telcos are paying much higher prices to Apple than they do to other manufacturers, in effect handing out extra subsidies for the iPhone. The question is how long this situation can continue.