Hardware is hardware. Period It's not about the hardware.
Well it seems to be about the hardware for Apple.
This is why they make their own cases/monitors/etc. and dont allow you to build your own machines. They want you using THEIR hardware only.
Not the entire truth...
UNIX systems maintain stability via strict control over the hardware they support. This is why most will only support the hardware they retailed that has undergone their expectations of test and quality assurance. It doesn't mean that they actually build all the hardware BUT they strictly try to limit third party because of a certain commitment to uptime / reliability that can potentially become a liability.
HPUX for example have sourced their SCSI cards from LSI and previously QLogic. The cards are then reflashed with HP's firmware which has been specifically tested with their O/S and drivers. This means that HP and only HP is responsible for the reliability of that operation. No need for HP to worry (and waste resources supporting) problems/issues that could have been introduced by some third party hardware, firmware, or software. Even if they could deny liability/support when unsupported third party items are introduced, it still sours the relationship between the customer and HP. Afterall, the HP-UX O/S is the most visable portion. Let's not forget that it costs $$$ to HP to even make that determination.
Ask any Windows IT guy... most have been stuck with a problem with Microsoft pointing fingers at the third party vendor and the third party vendor pointing fingers at Microsoft. It is extremely frustrating for all parties and very costly.
I have no doubt that much of the "Windows Sucks" experiences are steming from misbehaving drivers/software/firmware/hardware that came from other vendors and Not Microsoft.
On the other hand..
It is a double edged sword because it means you cut out most third parties which limits availability of hardware and support software. It is a trade off.. flexibility or reliability through stricter control.
Apple's treatment of MAC OS X and their hardware is following this model. The hardware they deliver is of higher than consumer level quality.. which costs. The only reason why it seems expensive is that there are no cheaper alternatives. Some would say.. its not that Mac hardware is expensive is that others are so darn cheap. Their laptop prices are on par with high end Sony's, Lenovos, HPs, etc... its just people keep insisting on a comparison with lower end Dells...
After a career experience in all sorts of platforms, I will say Mac can be as bomb stable as many production Unix servers I have worked on. The internals of my old G5 Mac workstation are definitely outfitted with good quality components for that time.
I personally think Apple doesn't much care for taking over the entire market from Microsoft. I think they perfectly happy remaining the niche alternative... doing well at it too. Let's not forget that Microsoft pushed out other competitors through business moves that limited availability to other O/S's... I'm sure Apple does make some $$$ from this same move... they are all guilty of it to a certain extent....