Because relatively few of them were made compared to other types of Model M's.
That's the only reason.
It's not a better keyboard. (Some would argue it's less of one because it's an SSK.)
There's nothing inherently cooler or more elegant about it. "Industrial" M's had gray cases to hide dirt better in dirty environments (garages, factories etc.). So in reality, its biggest distinction is that, while deployed, it probably collected significantly more dirt than most M's. It's like paying extra for a car because it was driven on dirt roads rather than highways.
What it's really about, is this: People like to have stuff other people don't. It makes them feel special. When you have a board like this, you can't do anything with it that you couldn't do with any other Model M. You just know that relatively few other people have boards like it.
But they do. Some people do have boards like this. Just not as many people.
And that's what, apparently, makes it worth over $1K: knowing you have a board that some, but not many, people have.
The blue keys are pretty, of course. Primates, apes as well as humans, are attracted to bright colors. Anthropologists think it's some kind of survival instinct, perhaps our ability to recognize water. Here, though, they're just little pieces of blue plastic; they wouldn't help you survive, unless you sold them to another obsessive person.
So there you have it—the real story, free of hype and hysteria.
Cheers.
