"Affordable" is a relative term. Affordable to you is clearly not the same as other people.I just can't believe the starting price is $2000 more than the previous Mac Pro.
As a current Mac Pro user, I cannot imagine being able to afford this currently.
These machines are meant for professionals—people who actually make money at their profession and these are the tools they do it with. These machines typically have a 7-8 year life. That's less than $1000 per year or $3 per day.
I think some "pros" need to raise their prices.
When you're talking about a full-sized PCIe tower like the new Mac Pro yes you absolutely can. Or find a local PC builder to assemble it for you. It won't look like a Mac Pro but it will be about the same size and, once its humming away under your desk, so what?
One thing you're missing there is OS Upgrades. People forget software dev also costs money. Apple hasn't changed for OS upgrades since, what Snow Leopard? Consider 7-8 years of upgrades at $129/year and tack on another $1000 as well. I'd pay double not to have to use Windows.
Apple is a hardware company but people also forget that their ongoing software dev needs to get amortized in the cost of the hardware somewhere.