Speaker depreciation: Is there a rule of thumb?


I'm looking at used speakers and wondering if there is a 'rule of thumb' for determining a fair price. I imagine (operative term...imagine) what kind of reviews the speaker received after manufactured, materials used, age and other factors have an impact. Your thoughts?
128x128mdrummer01
The rule of thumb is never to buy new if you can buy the equivalent second hand.Hi Fi gear can depreciate rapidly.If I buy second hand I look to buy it for a third of its new retail price and if the product is more than 3 years old this is very often possible.It needs to remembered that when people come to sell second hand they like to quote the retail price but rarely does anyone actually pay this price.

JT
I have noticed that the depreciation in addition to age is size and brand dependent. Big unknown speakers you are lucky to get 50% more likely 30% of oringinal msrp. Small easy to ship speakers from a well liked ,popular brand, you see a lot of people asking for as much as only 30% off of msrp, just the opposite.
Markphd makes a good suggestion in my experience: Follow the listings for a while. I have found the AudiogoN blue book to be generally high in average price. I am currently watching the Sony SCD-1 market, and missed a good one because I had not updated my email address on AudiogoN so the seller missed my what-would-have-been-winning bid.

db