Even for a rare model? I see them going for that much quite often. I buy them for that much often enough if the model interests me and my research and buying experience lead me to believe that it is hard to find. Typically, I pay that much only when the rare watch has already been cleaned and restored, but there are exceptions. But then, I'm not a conservative buyer by any means and probably not typical in that regard.
I don't know your listings, but I assume that you take good photos, provide all the essential information, and write professional-sounding ads? Many don't, and my guess is that hurts their sales.
In the end, I think it comes down to how rare the watch is. Cleaning and refurbishing can always be done later, but you may never get another chance to buy that particular model. I think it's that fear that drives the price.
Also, I should add that sometimes it's just an accident. I can't always be there for the end of an auction, so, to foil the snipers, sometimes I'll put a really high bid limit just to be sure that I get the watch. Occassionally that strategy bites me on the butt, such as when I come back to the computer later and see that I just paid nearly $300 for a watch that I didn't want all that bad.