What is the model year(s), technical, and other differences, 
between the two following Sony LCD television sets?   

60 inch Grand WEGA™ Rear Projection Television 
KF-60DX100  
The Sony price Is:   $ 5,999.99

60 inch XBR Grand WEGA™ Rear Projection Television 
KF-60XBR800
The Sony price is:   $  4,999.99

clicker5,

Thank you for your question.  I scoured and scoured looking for
differences in these two models.  On paper, the only differences I
saw, based on Sony specs, is, though a newer model, the KF-60XBR800
has improved contrast, Memory Stick Playback and DVI-HDTV interface. 
That being said, I think your key question is why, with a few more
features and otherwise identical specs, is the XBR800 less expensive
thant the DX100.  There are a couple of reasons for this.  First, a
basic tenent of technology is "more, cheaper".  Look at any technology
and as it manifacturing improves, the demand increases, etc.,
companies add more and make it less expensive.  A great example of
this would be the computer industry. I worked for a major manufacturer
of computers back in the early 90's.  We came out with this hot new
computer:  the 486DX2-66.  Standard configuration was 16MB RAM, 800MB
hard drive, 15 inch monitor and a 28.8 modem.  You could have had all
of that for the low, low price of $3,995.00.  Now, obviously that was
years ago, but it gives you an idea.  Look at DVD players, Camcorders,
any high tech item, in which this TV falls, and it comes down to more,
cheaper.

In researching, it also appears that the XBR800 is manufactured in the
United States as opposed to Japan which may also account for the lower
price.

Enjoy your new television!  Thanks for your question and if you have
need any additional clarification, please let me know.

Regards,

-THV

Search Strategy:
KF-60DX100 KF-60XBR800

References:

KF-60XBR800 Specs
http://www.sonystyle.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_DisplayProductInformation-Start;sid=U7XN7-EaWybN798fYlnH5K4KRR7zim1GO7s=?ProductID=O1AKC0%2eN1EMAAADyZ5w8lSwg

KF-60DX100 Specs
http://www.sonystyle.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_DisplayProductInformation-Start;sid=U7XN7-EaWybN798fYlnH5K4KRR7zim1GO7s=?ProductID=rUMKC0%2eN9zcAAADya1I8lSwg

Audio Video Forum
Sony Grand Wega KF-60DX100 60 Inch LCD TV
http://www.audiovideoforum.com/forum/showthread.php?s=a4420f7e36d355b1aaecb87763fefb5a&postid=572#post572

Ecoustics
http://www.ecoustics.com/bbs/messages/2/960.html

Thank you, for the first-rate research.
I looked at all of the web sites you pointed me to, and each one added
to the complete answer.
Again – good job.
I rate you with 5 stars.
Clicker5