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