Since many other brands' of mobile devices( both phone and tablet) have come to around 1.7 or even over 2 Ghz Quad Core, Less than 7 mm thin, 2 GB RAM, even for the retina parts (some has more than 400 PPI on screen)
iphone 5S 326 PPI
ipad air 264 PPI
Читать далее: Why are iphone 5S, ipad air only around 1.4 GHz Dual Core, 7.5mm thin, 1 GB RAM?