Fair price for used B&W DM603 S3?

Hi there, new to this forum, I have a question. Recently I found a used set of B&W DM603 S3 fronts, DM600 surrounds and DM60 CLR Center. The guy want to sell it for $900, but I'm not sure what is a fair price for them, as they are 5-6 years old and cost $1500 when new. I initially agree with the price, but having second thought as $900 is a little high for these.

Thanks for your response.
You can look it up on Orion Blue Book or maybe try searching sold prices on Ebay.
I'd do it as long as the dm600's and the dm 60 were s3 models also. You want them all to be of the same generation so they match up tone wise. I think $900 is a fair price. If his asking price is $900, offer $800 and go from there, but I do think $900 is fair. By the way, what made you think that price was high? Did you research used sales prices or did you just "feel" that price was too high because you just felt that way?
That seems way to high.He is lucky if he gets $600.
A six year old speaker at $1500 list that he must of got at least a 10 percent discount when new if he was original owner. How do you know how many times they have been sold? I think $700 is the most I would offer.Good luck!