They are great speakers!
Tok20000 is correct. Very hard to find used and supposedly a great speaker.
You just might see one used pair per year for sale on the used market. Last summer there was a dealer demo pair on agon for $8500. I had inquired about them for a friend.
Perhaps next summer there will be another pair.
Because of their calibur and quality and the usual supply and demand theory, I would think that for a 2 year old pair, anything under $8500 is probably not worth complaining about. So long as they are in excellent shape and you wish to move quickly realizing you might have to wait a while before you find another used pair.
If you are impatient, you might want to consider combining Vandersteen model 3asigs with two 2WQ subwoofers. the 3asigs have the same tweeter and midrange driver as well as other technologies embedded in the model 5s. There are several people who have taken this approach with very satisfying results (they claim to achieve 85% of the performance of the 5s).
You can find the 3asigs used for $2500-2700, however, you will probably need to purchase the subs new. I have also read that it pays to purchase the model five grade filter to insert between amp and pre for rolling off the VLF sent to the mains and redirecting to the subs. This filter is better than the stock unit sold with the 2WQs.
You can find info on these options in the archives. That is where I learned about them. I, myself, own the 3aSigs.
I've seen used ones for around 50% of retail, but it's true they don't come on the market that often. If you have a pair lined up I wouldn't pay more than 5 to 6K in this market. There are many great speakers selling for well below 50% of retail. The Talon Khorus is an excellent example of a great speaker that's being given away due to our economy. Also, keep in mind that in order for the 5s to be properly set up you will need the test equipment that is provided by the dealer for adjusting the woofers response in your room. If you have not already done so read Robert Harley's review in The Absolute Sound. He covers this in some detail. As another possiblity you should go to the VMPS website (vmpsaudio.com) and read Martin de Wulf's and Peter Moncrieff's reviews of their RM-40. I too was very interested in the model 5s until I read these reviews. Two of the best reviews I've ever read on loudspeakers (and I've read a lot) and both by excellent reviewers with publications that do not advertise...they tell it like it is. Check it out.
I have had my eyes open for a used pair of Vandy Model 5's for more than 18 months, and only seen one pair for sale here on Audiogon. The seller (in New Mexico, as I recall) was having a hard time finding a buyer, and he had reduced his price to $6750, which is the lowest price I've seen for the Model 5's. For a relatively new pair, I'd expect to pay around $7500-8000 for the base model in oak veneer (the sexy wood veneers will run more).
If you don't know this, Vandersteen has just released the upgraded Model 5A (see the link below for more info). The release of the 5A may result in more of the early Model 5's coming onto the used market, and perhaps at lower prices.
You might try contacting John Rutan at Audio Connections in New Jersey. John is, I think, the highest volume Vandersteen dealer in the country, and he gets a lot of speakers traded in.
Link for info on new Vandy Model 5A: http://www.vandersteen.com/pages/Model5ALit.htm
Because of their weight-- 225 lbs. each when packed on their own pallets, and the difficulty packing and shipping them, I think the Vandersteen 5s can be difficult to sell when shipping is involved. I'd guess that most are sold with some kind of local pickup arrangement. For this reason, I thought long and hard before I bought mine, and I intend to keep them indefinitely. They are wonderful speakers. Good Luck. Craig