An item, any item (car, watch, art, audio equipment, camera, etc.) is worth exactly what someone is willing to pay. Regardless of what you feel the item is worth is really irrelevant.
You can post the item and list a price and the negotiations start from there. If you are firm in your price, then say that, and ignore anyone that lowballs.
If a buyer is really serious, then they will contact you with a serious offer.
I collect rare books, watches, classic cars, etc. I can tell you there are two types of buyers. 1) the collector and 2) the dealer.
The collector wants that item and is willing to pay near or above market prices for that item. The dealer simply wants to flip the item and therefore, they want to pay pretty much nothing for it, then turn around and flip it for as much as they can.
No difference in the audio industry here on audiogon. You don't know whom you are dealing with. I try to not be desperate to sell something and therefore, I can list the item at what I feel is a fair price based on market values. Maybe slightly lower than the average market rate and I typically have no trouble selling the item.
I ignore the lowballers that come in with stupidly low counter offers.
Someone will eventually want the piece.
enjoy