They're big, expensive chips with a focus on power efficiency. AMD and Intel's chips that are on the big and expensive side tend toward being optimized for higher power ranges, so they don't compete well on efficiency, while their more power efficient chips tend toward being optimized for size/cost.
If you're willing to spend a bunch of die area (which directly translates into cost) you can get good numbers on the other two legs of the Power-Performance-Area triangle. The issue is that the market position of Apple's competitors is such that it doesn't make as much sense for them to make such big and expensive chips (particularly CPU cores) in a mobile-friendly power envelope.
If you're willing to spend a bunch of die area (which directly translates into cost) you can get good numbers on the other two legs of the Power-Performance-Area triangle. The issue is that the market position of Apple's competitors is such that it doesn't make as much sense for them to make such big and expensive chips (particularly CPU cores) in a mobile-friendly power envelope.