The final assembly for a CTO would be done in the USA for an order meant to be delivered in North America. For Europe, it's done in Ireland.
Not sure this is universally true. I've purchased a personal CTO 12-core last year, and 3 more for business use this year, and all of them were "assembled" in Shenzhen (which really amounts to what exactly, popping in 5870s and upping the base 2.66 to 2.93s in two cases). <-- not done in USA though, tracking just showed direct hop to Anchorage, and delivery, in all cases.
Dell, HP and other PC vendors are willing to use discounts and/or incentives to help move systems, and I've even gotten better pricing over the phone than the web site on numerous occasions over the years.
Agreed, other than the random Best Buy/Walmart unloading iCrap at below cost, every single human being who can flash any kind of college ID, gets a discount at every single Apple store on Earth. If you're buying personally, you can also get the rather nice 25% EPP discount if you happen to do work for Apple (or have a friend who does). If you want something which is in short supply/white-hot, you may have to wait a month or two before the EPP has it; but Mac Pros are always available immediately, it's not like there is a mass stampede to buy the things and highly limited supply with overwhelming demand <-- has never happened in the past half decade. 25% off an iPhone or iPad, amounts to meh, but chop that price off a Mac Pro loaded up with ACDs, and it's pretty significant.
While the EPP may not be a viable option for most people, as nanofrog said, you'd be surprised what just picking up the phone and talking with a human being can accomplish (especially if you are making corporate purchases), and if none of the previous apply, surely you can find one college student/faculty member somewhere within your social circle (please insert avalanche of, "ohhhhhh, you're a bad bad bad person, nobody should do that, it's morally and ethically wrong!" rants [here]. The response to which is, from my end anyway <shrug> I don't really care, and I'm a shareholder with a f--kton of Apple stock, feel free to notify the karma police, a hall monitor, and your mom).