A phone is a commodity with little technological known-how required to pull off today.

iPhone sells for $1000 because people will pay so much for it but that doesn't mean that the technology in it costs so much.

However, when a single diffraction waveguide (the piece of glass that forms the display of devices like a Hololens or Magic Leap) which is the only known way how to make a flat-ish display (otherwise you need bulky mirrors or prisms) costs hundreds of dollars (and you need 3 per eye minimum, one for each color), then it is hard to see how Apple would pull that off. And that's only a display.

At least if we are talking a proper AR device, not a personal HUD/"smartglasses" like the Google Glass.