Price? Intel charges hundreds of dollars for their processors. Imagine how much cheaper ARM Macs would be? We already saw the result of Apple depending on Intel for processors - they couldn't launch new iMacs last year, screwing up their whole release schedule which I'm sure Apple lost millions of $$. Additionally, we don't know that Apple is even going to use the same ARM chips in Macs as they do iOS devices. They might be designing a whole new desktop chip.