hifishark came up. One pair of Venere 3.0 speakers in walnut finish for sale now on USAudioMart for $2,150 (minor damage) and an expired dealer listing on the same site from Nov. 2016, for $2,400. List price was shown as $4,000. I filtered expired listings by country (USA) and found 40 expired listings showing typical used "asking" price mostly between $2-3K. If you want the "selling" price, reduce asking prices by something like 10-20 percent depending on age and popularity of the product, condition and other factors such as finish or color, sales terms, shipping distance, etc.
One thing hifishark has over the A'gon bluebook, in addition to searching multiple listing sites, is that you can open the actual expired ads and see things like photos, condition, and special considerations in the seller's write-ups.
dill, I don't understand your comment that hifishark is not a good source for high-end audio. I searched Wilson, Boulder, and D'agostino, and all were well-represented. Hifishark doesn't have their own listings but works like a search engine that simply links the actual listing site.