My years in this hobby meant buying and selling lots of equipment. The basic rule I use when selling is to begin at 50% of retail, then adjust up or down based on some basic factors. If the component is current, in near-new condition, has brand reputation, or collectible, then I adjust the price upward by whatever I consider a reasonable amount. If the component is no longer current, has any cosmetic or functional issues, is little known, or, most importantly, if the manufacturer is no longer in existence, then I adjust my price downward.
Also, as I've commented previously, I consider the Orion or Bluebook values to be under market. I suspect they may be oriented to give dealers a rationale for more modest trade-in values.
Hope this helps and good luck.
