Audio valuations

Is anyone else interested in determining a fair value for used high end equipment? I understand we all try to sell and buy our equipment at the best price, but where to start? I recently listed
a item for sale and set a price that I thought was competitive based on very limited past sale information. I did receive an offer that was $500 less than asking price. Was I too high or was the offer too low. It would be helpful if we could see what others sold their equipment for and the condition of the equipment. I want to sell my equipment, but I don't want to give it away.
Any thoughts on this matter?
I always look at hifishark and ebay's completed sales before I buy or sell anything.
elf1, you have been lowballed.  The 6b goes between $1000 and $1100 normally.

Lots of 6 series ARC preamps sold, and an active used market.  Audiogon's Bluebook lists them all, and eBay sales, Audio Mart, and other sites tend to agree with the values posted there.

This series goes approximately as follows:  6, 6a - $900-950; 6b - $1100-1200; 6c a bit lower, and the all-tube 8 around $1300-1500.
One of the lucky transactions that I actually made money on. This is the exception to the rule.

I just sold a pre-owned, discontinued mint SACD player for more than list because the buyer, who is very happy, has a large collection of HDCDs. At first he asked a ton of questions but then I realized he was serious.

(The new models won’t play them. Does anyone know of current production model that will play HDCDs?)

There are always lowballs out there but some folks stick to an unreasonable price. And there is fashion to contend with. I wonder if the prices of AJ Conti and Ayre equipment will go down drastically since the eponymous founder has unfortunately passed away?
While the A’gon Bluebook is a fairly valid reference point for determining what is a “fair” price to sell something at, that it doesn’t offer an insight as to the item’s condition at time of sale leaves a pretty wide degree of latitude for making offers.  Without that to take into account,  relying upon a seller’s personal evaluation of an item’s operational and/or physical condition is debatable and as justified a starting point for negotiating as any. 

I do research prospective purchases from fellow members whether they be individuals or retailers. I use the averaged value as a starting point - after all there is no weighted average for 7/10, 8/10, mint, etc. 
I also deal exclusively with fellow members who, like myself, have 100% positive feedback.  That goes a long way toward determining what I may offer. 

We all want to fetch as much as possible when we sell something here - human na’cha!  I just purchased a Modwright KWI-200 integrated here at the seller’s asking price without negotiating because a.) the seller had 100% positive feedback
b.) because I had been reading a lot of excellent opinions on Modwright in general
c.) because the A’gon Bluebook average was spot-on

The seller did not describe the item as “mint” but it certainly was.  Impossible to discern from new. 

A little research goes quite a long way into having pleasurable transactions here