What jperry said....
Also you can search here (and on AudioAsylum or USAudioMart) by brand and/or by type of equipment to see the asking price for similar gear, which can help with your pricing strategy. However, keep in mind the asking price is not necessarily an accurate indicator of what people are selling for. Also, "fair value" is really arbitrary and frankly doesn’t mean much if there are no buyers willing to pay the "fair value" price you are asking. Sometimes, it just takes patience and that "one best buyer" to come along and want the gear you are selling.
There is a lot more that enters into successful selling here, such as your willingness to hang on if there are no ready buyers vs. how bad you need the cash, condition and owner history of the item, the time of year, whether the item is likely to hold its value (i.e., many amplifiers), whether it is over the hill and sliding down the depreciating side of the curve (i.e., digital gear), or whether it was a flash-in-the pan item that has subsequently seen a lot of competition (i.e., USB doo-dads for 5V and/or galvanic isolation, certain types of footers, and other tweeks). The manufacturer can make a big difference too. If many units of the item were sold (i.e., think Ayre gear) there are likely to be many other sellers so then the item is more like a commodity and the condition and price will be more likely to govern the sale. If the manufacturer has a propensity for constantly releasing new models, their gear may not hold its value simply because people will anticipate a short life-span before the next new thing comes along (Lamm would be the opposite of this).
Finally, your willingness to accept risk enters the picture with respect to whether you want to sell through a website with no feedback criteria, and whether you are comfortable selling to an unknown buyer with no feedback. Audiogon offers the ability to at least observe the buyer’s buying/selling history, whether they have negative feedback (and why), and how long they have been around. As the seller, you can choose who you sell to (although you should clearly define that in your advertisement). As one example, I require higher standards for my buyers (i.e., no newbies, no negative feedback, must have positive feedback, no proxies, no sales out of the USA) when I am selling big-ticket items than when I am selling cables. Whether you are willing to sell overseas or not is another issue - I have been successful doing this but there are usually fees, it takes longer, and if something goes wrong it is much harder to rectify. Finally, if there is one thing I recommend it is to over-pack and, for big items strap them to a pallet and ship freight since everybody loses if there is shipping damage.
