" And why would I buy an RT tablet for more than I would pay for a Bay Trail tablet that runs full windows?"
simple, for the same reasons people buy more ipads over everything. some people like the simplicity of it. there are people scared away from more technical aspects of the full blown OS. plus the RT line is more secure. You should be asking Delta airlines this question then..

as they see the Surface2 line more than fit. I think they were originally considering Dell but MS beat them out.
Don't forget "value added." Windows RT comes with Office 2013 RT, and that's a pretty big value added. For a fair comparison on base device spec without extra software, you'd have to subtract $$$ from the Surface RT devices or add $$$ to the Win8 devices (for consumer use). Corporate accounts are going to add the devices under umbrella licensing, but that's neither here nor there if we're talking about individual choice anyway.
For non-commercial use, the separate Office 2013 applications are officially $290, add $100 for Outlook. Around $200 for the box. If you're a student, you can luck out with a $80 Office 365 subscription, but I hate the idea of being forced to "call home" every 30 days, and I like to keep my software for a long time if it's working for me. 365 is $99 a year otherwise, so if you plan on keeping your device three years, subtract/add $300 from the WinRT/8 devices for comparison.
Some people will buy the Dell, but they are plastic and Intel's track record with Atom SoC is suspect.
The Surface 2 is the thinnest, highest quality tablet being released. The Surface Pro is using Wacom Digitizer and Dell is using a Synaptics First Generation Digitizer which s touch first and pen second, questions remain on the Digitizer's effectiveness for daily inking.
Honestly, when I first opened the box for my Acer Iconia-whatever, I was immediately disappointed by the plastic. Very cheap. It has flex. My very first subnotebook was in full magnesium alloy casing, and then its replacement was mostly plastic, but even that plastic was "higher quality" (I think the IBM thinkpads were also plastic, but you can tell the quality difference).