Apple is a software company fundamentally. What makes a mac different from a PC is OS X. What makes an iPhone different from an Android phone is iOS. The hardware is basically the same underneath. So Apple sells you their software but won't sell it without a fairly nice device to go along with it. However an important feature in this is that Apple has design chops and retail experience in their DNA. Microsoft doesn't. So Microsoft has to replicate what Apple is doing without the design culture that makes Apple successful at doing it.
I'd have to disagree with this. While the major components of a PC are no longer designed and built by the manufacturer (CPU, memory, drives), Apple does do more with hardware design than the next manufacturer. Sure in PCs, they don't design their own CPUs but they still design motherboards and the overall case. While the like of Dell and HP and Lenovo offer very bland models with little differences, Apple does make some interesting design choices in their computers.
For example, the Macbook Air is Apple's answer to the netbook. Instead of shrinking the whole laptop in all dimensions (and making it hard to type on), Apple went thin. Now that seems like there isn't much engineering but to make it thin, Apple did have to design motherboards much smaller, use customized Intel chips, use SSD instead of HDD in laptops years before it was the norm, remove many I/O plugs from the case. These were not without criticism but years later and after refinement, the MacBook Air is the direction almost all PC manufacturers are going with.
Another example is the MacPro. The newest version is dramatically different than other workstations. First of all, it's not boxy. There's little expansion. It uses PCIe SSD drives. Cooling wise everything does up instead of through and the main components are separated on 3 different boards instead one motherboard.
Controlling the software does make Apple better at integration but Apple does make an attempt at hardware differentiation.