I think that there's some collectors that just really don't mind shelling out serious money for the music that is their passion. But I think that for every item that commands such high prices, there are dozens for which it was asked where they don't sell.
Now, since we're doing this as a shocker non-log, I figure I'd put one in - the Esoteric SACD on Antonin Dvorak's 9th Symphony (AKA the New World Symphony) recently sold for $869 on eBay. This is a stereo-only SACD, about 40 minutes long, and it came with the OBI. Link:
http://www.ebay.com/itm/252326448521
From my perspective this is categorically insane...you can get numerous excellent recordings in excellent sound, with superior orchestras to the 1960s Vienna Philharmonic, which was still emerging from an era of postwar relative mediocrity, with conductors with their own insights to give - and with more music on the CD. Just to start you can get the Living Stereo SACD of Fritz Reiner with Chicago new and shipped for $10 (2 and 3 channel), and the modern DSD/surround recording of Ivan Fischer and his Budapest Festival Orchestra performing both the 8th and 9th symphonies for $17 new and shipped.
But clearly different people have different priorities. The eBay bid log shows 3 different bidders, all of whom were willing to pay $800 or more. For some people money is no object to having the ultimate version of their favorite recording. And while I don't share that attitude, I'm not sure I could fully refute it either.