I remember when they came out, the SO guy carried it in everywhere for show and tell. Apparently they don't make them any more. I also wondered what they were worth, got one in a box I bought. I put a price tag of $40 dollars on it, hasn't sold yet but I'm sure it will.
MAC has made some of those indexing ratchets too - they even put out a combination flex-head/indexing - but they never caught on in popularity very well.
I have one of those (the Snappy 3/8 version) - a Christmas gift from mom a few years back. Terrific tool. You can index the head, leave it unlocked and use it as a speeder, or just leave it straight and enjoy the 72 tooth action (so it clicks every 5 degrees).
Tight spaces are its highest calling. If I had any use for a second one, I'd be interested in that auction for sure.