We do need this in a separate thread, don't we?
@TTJ also raises a good point about robustness - all my DIY builds are cases made out of lower quality (thin) tin-like metal but our servers at work are solid steel that don't flex when you pick them up and have all named components inside, not low spec unbranded parts. As you say; Entry level vs pro build quality.
As for CPU's lets keep the differences simple:
Core i (then a number) CPUs from Intel are designed for desktops and Xeon CPUs are designed for servers. The Xeon CPUs do more, run hotter, have stuff that interfaces internally that is more likely to be in server gear than in end user gear, they are supposed to do more, be faster and so on, but also cost more.
Clock speed isn't the only thing that helps with performance. With the Xeon range where you have more cores, you also need more top speed cache RAM on chip too or the thing maxes out earlier and you don't realize the throughput potential. This costs more to make - way more to make - and lets also not forget that they are also charging for gear that will go into a $8,000 box that will run 100 concurrent users, not a $700 home-brew single-user machine.
Being cynical, remember in the capitalist system, someone has to make obscene profits too! Bwahahahah....
I can't disagree with any of that. After traveling for years, used so many desktops, so many laptops, that I have seen $600 business machines out last $2,000 "gamer" systems from over heating etc. Upgraded power supplies, chassis, robust chips, vibration reduction mounting hardware, drives made for abuse or massive write/rewrites, etc. Panasonic, HP and Lenovo(thinkpad) business class PCs laptop/desktops seem to be the best with Thinkpads having the only options for "super user" mix in them. You pay more, but with less down time.
Here is a link I think everyone would like. Someone tests most all processors - Laptop and Desktop. It is really interesting to see that my 5yr old processor (based on CPU benchmarks) by this out performs some early i7s mobile processors. It is the only easy info site where I have found Laptop processors lined up against desktops. My processor is highlighted. Neat info really.
Now there is a ton more that goes into a good running machine than just processors but for me, I want to at least double the "whole" machine when I upgrade. The "other" numbers for me are easier to understand speed increases - processors are rather cryptic I find. I haven't taken the time in years nor really care that much to learn it either. I'll rely on others to do that for me, and get the results from them.
For those with PCs, I have been reading that Windows 8 is going to need 8gb to run, and is best with 24gb+ of ram with sata 6gb/s drives. I'm sure they will sell machines with less but one thing we can always count on is when Microsoft releases a new OS, that very few mid-lower end current machines can run well with it. XP and Vista support will be dropped at that point as well. It sounds like Win 8 will also require many software vendors to re-write their programs. No clue where Adobe fits into that.
Thinking of stuff, anyone have a good link to a article on using two machines (laptop/desktop) using LR4 and how to transfer the edits from one to the other? Example: traveling with a laptop, edit some files on the road, but then wanting to transfer all the work to a master LR4 on a desktop. I wouldn't mind a 13" ultra book and use a desktop for major stuff. Anyone do something like that?