Well I did my my ARP AXXE on ebay 3 years ago for $250.00. And I bought my OMNI from a Pawn Shop for $150.00.
I have gotten lucky on ebay a couple of times, but 800dv is right that there are people who are dumb enough to pay a high price just to get on particular item. Especialy with ebay expanding and reaching a broader audience.
Although buying from a Music Store or a Pawn shop is not easy for some people, who may not live near a music store or Pawn shop and have to rely on the Internet. I had one bad experience with a Pawn Shop my omni was dead, but they told me it worked. Big mistake, I should have been more assertive. But I did get it working, but it cost me $195.00. Plus it now has two dead keys. Plus finding vintage music gear in a music store is getting harder too. I live an hour form Baltimore MD in Frederick MD. So I usually go to Bill's Music house I have seen a few vinatge peices ther but not many. Usually one or two. I remember back in the early 90's when vinatge synths were not popular they had several vinatge synths. Of course I did not have the money at the time, and a lot of their used gear tends to still be price high. Well more then I am willing to spend. So I keep looking until I find what I want at a price that I want. Even if it's ebay, or a music store.