It's just about my favourite lens. (Well, besides the 7-14.) It is incredibly sharp and contrasty at macro, infinity, and in-between. It has an extra mechanism for a moving element group that is engaged in the macro range, which might be how they achieve such a feat. It focuses to half-life-size (1:2) without any extension. I find it also works great with an extension of 116mm, which is the Olympus Telescoping Extension Tube, fully extended. (Some macro examples, both at 1:2 and with 116mm of extension, are here.)
The kilobuck ones are typically mint. Sometimes you can find "brassy" ones with perfect optics for half of that. But because of their collectable status, they seem to go nuts on evilBay. If you're looking for an inexpensive copy, you might do better with KEH, or periodic queries with the New York camera merchants that carry a good selection of used gear. My notes say I paid $650 for mine (not mint), nearly 20 years ago. So they have held their value!
Whether or not they are "worth that much" is a personal value judgement. If I didn't already have one, I'm not sure I would spend that much on one today, but since then, I've left high-paying high-tech work and taken up farming, and watch my money much more closely. If I had a good paying "real job," I might feel different about this lens.
I would say it is certainly one of the world's great lenses, so the market price is really a bargain, compared to some Zeiss or Leica glass.
I wish you hadn't said that, well the part of me that controls the bank balance does.
However the part of me that covets fine glass is very pleased with your reply.
Now, shall I sell something or just go a bit deeper in debt ?
PS there's currently 28 listed on eBay, ranging from $547 US to $1455 US. That's almost $2K in our funny money.