I think the argument of Apple's build quality and design is extremely valid. I'm on my 3rd MBP now and I've followed roughly a 2.5-3 years upgrade path. Haven't had a Windows machine since OSX 10.1, and I have to say, none of my Windows based notebooks have ever lasted as long as my MBPs and I had to buy a new one every year or so. Thus really from a financial perspective, the MBP turned out cheaper for me since by the time I'm buying a new MBP, i'm already on my 3rd Windows based notebook.
I used to be the CTO of a fairly large IT company, and I did notice that the frequency of Windows notebooks breaking and people requisitioning for a replacement is much higher than the MBP users (ratio-wise of course). I did a cost analysis run, and was pleasantly surprised that if I switched all 2700 stations (desktop, notebooks) to Macs, in a 3 year run, I ended up saving about 300 dollars per station, assuming no breakage, that would equate to about 810K in savings. When I factored in the frequency of breakage, that number goes up to an average of 800 which is about $2.1m. Unfortunately Microsoft was just too entrenched in that organization that it would require a concentrated effort to make the change that had too many variables. Now if I were to start a new company, I'd start it based on the Mac platform to begin with.
Lastly I would wager that 90% of the users out there and their computer usage patterns, a 3 year old Mac is still plenty fast for what they do. Its really the power users that are annoyed at Apple's slow pace of component upgrades, and the reader based of this site is mainly power users. However I would bet that 90% of Apple's customer base or any hardware company like Dell, would not be power users like us and thus will really see minimal benefits from their perspective. What drives them to get an Apple is really for the design and of course OSX.