Those are good recommendations for selling, I watch Astromart, but have not seen their auctions. They have a classifieds, and anotherAstroMart has a binocular auction-you might try that.
BirdForum also has a sell section.
My issue with the WXs are too expensive, too heavy for practical use and there are many 10x50s almost as good that are easier to buy and use;
but they are the best binoculars available.
I agree with the above opinions that they would sell for $4000-and maybe more.
active place to sell is on Cloudy Nights classifieds which is free.
The Nikon 10x50 WX is an astro binocular, so it has a special market.