What's up with the Nvidia Quadro?

[{NcsO}ReichstaG]

Okay, I was flipping through the pages of a "TigerDirect.com" catalog when I saw the "Nvidia Quadro by PNY Pro" sell for outrages prices.
{Moderl #: P56-FX1100} Quadro FX 1100 128 MB (dual dvi)...$699.99
{Model #: P56-FX500} Quadro FX 1100 128 MB (dual DVI/VGA) ... $250
{Model P56-4280} Quadro 4 NVS 20 64MB AGP (Dual/VGA) ... $199.99
{P56-FX700} Quadro4 128 MB (dual DVI/VGA)...$599.99

Question number one:
How come "{Moderl #: P56-FX1100} Quadro FX 1100 128 MB (dual dvi)...$699.99" and "{P56-FX700} Quadro4 128 MB (dual DVI/VGA)...$599.99 " are so expensive? They are more expensive than either the 6800 ULTRA or ATI XT-PE and both have only 128MB of memory.
What is so special about these cards that other cards do not have?

Question number two:
How come even though "{Moderl #: P56-FX1100} Quadro FX 1100 128 MB (dual dvi)...$699.99 and "{Model #: P56-FX500} Quadro FX 1100 128 MB (dual DVI/VGA) ... $250" have the same name "FX 1100 and 128 MB" their costs are like night and day? Is it because of the dual DVI and VGA?

In general what are these cards utilized for?

Also what does this mean:
"Unprecedented price performance for professional 3D applications" Wait a minute, I thought the 6800 GT has good 3D performance and it does not cost either $700 or $500.
"128 MB 256-bit DDR"
"Fully programmable GPU"
What does that mean: "Fully programmable GPU"

 

[inotocracy]

There used for CAD and 3d modeling programs.

 

[{NcsO}ReichstaG]

Can't a GeForce 6800 GT for $400 or an ATI XT for about $500 handle the same 3D modeling applications? They are used in [H]ard gaming..right? Who would pay about $600 or $700 for a Quadro?