You just don't get it all do you?
No, clearly
you don't understand. Apple doesn't compete in the sub-market you're asking for and won't! It doesn't work within their business model! It's as simple as that! The ad hominem statements you've made here as well are unwarranted -- watch it.
Regardless, I've used Windows and Linux at least twice as long as I've been using OS X, if not longer, and have built plenty of my own PCs, so I understand the want for a cheap, expandable box. At the same time, I don't pretend that's the majority of the greater computer market out there. It's not. Joe six wants cheap. Not expandability, not $600-fast video cards to play games, not extra hard drive bays to run backups onto. For those that can cross out the cheap, Apple has a great lineup. For those that can't, there's always the competition. For those that want the proverbial, enthusiast-level xMac, you're not a large enough market, sorry. Apple's selected the people they want to sell to, because they know how to make an excellent bottom line that way better than you can on the commodity, beige box PC front. End of story. Although, if you can get them to shift Mac Pro prices like CWallace suggested, then maybe you have something.
Also, don't make statements that you have no hope of backing up with any logic or evidence. Really, nice, suggestive crack there about Windows/Linux/Mac OS experience, but the insinuation behind it was uncalled for (and false). And, if your argument was done correctly, it'd acknowledge that, while internal hardware may be the same variety (of CPU, RAM, GPU, HDD, etc.) there's more that Apple does with their computers besides those things that set the Mac apart from the garden-variety PC. It simply isn't just the OS. There are other value-adds.
Pretty cases aside (you can get very pretty customized cases in the Windows and Linux world you know), the hardware is all the same except that most of Apple's "desktops" are really "laptops" inside a flat screen monitor case. Desktops should use desktop parts which generally smoke laptop parts, which explains why the MacPro is so much faster in so many areas. The problem is the average consumer doesn't NEED pro-level parts like 4-8 Xeon cores. Apple could easily reuse its existing case with consumer level parts to offer an alternative to the iMac in the $1500-2000 range, but they choose not to because they make more money forcing you to buy a MacPro at $2300-$4000+. The only other headless Mac is the Mini and it's not even competitive to the cheaper iMacs. That's not a different market. That's a choke hold.
You clearly don't understand the value-added points of each type of machine that Apple makes, nor the people they're intended to be sold to, and why, as a BUSINESS CASE (nothing emotional here!) Apple chooses low-volume, high-margin upper market products (all except the Mac mini, perhaps) over your beige box. The parts inside are hardly the main point -- lots of people on forums don't understand that the geek specs aren't everything (cars aren't only made of engines!). Your little spec comparison there is pretty irrelevant in the grand scheme of Apple. For the most part, they only need to differentiate between consumer and pro, and they do. Other things about their machines besides processor type take it from there. Not to mention -- the reason the iMac gets "smoked" by the Mac Pro is because it uses
workstation parts. Last I checked, that was in another league than desktops.
If they really wanted to sell mid-range and low-range generic boxes, they'd become a high-volume, low-margin company like Dell, HP, et al. But that's an entirely different type of business, and if one takes a look at the greater business world, it's not hard to spot these two different approaches in other industries -- not just this one. As Apple's strategy is, moving away from what they're currently doing would only end up diverting their resources away from more lucrative products that they sell (and fighting for pennies on commodity boxes is not lucrative! the high margins on their other products are). They aren't set up to compete solely on market share and price. Thankfully, there's more dimensions to competition than that. Unfortunately, many people don't realize that. So, if you honestly think that Apple can move into churning out super-mass produced generic boxes and not have a harmful restructuring of their business, I've got a bridge to sell you. Furthermore, if you think they'll sell enough $1500 enthusiast boxes to "cries of Mac forums," I've got three more to sell you. But I hope you don't actually need bridges.
If you want to continue the argument on CASES, go right ahead, but there's more cases than "pretty" just as there's more to computers than CPU/RAM/HDD/whatever. Overall good design, integration, attention to typically neglected pieces of hardware (what beige boxes typically come with H-IPS screens? Apple sells these on the 24" iMac and cinema displays) are all important parts that are being ignored here that Apple pays attention to, among other things. Apple has no reason to compete directly against those products that typically ignore that and where the calling price is "cheap."
The position they take now is good for themselves
and the greater PC market. It brings other options to the table by a company that executes them well.