Suppose your band is about to take off, so you go out and buy a brand new Marshall Tube Head and Cabinet amplifier for the list price of about $4,200. Your band immediately breaks up after you've used it only once.
You hang on to it for a year or so in case your drummer and bass player can work out their differences, but it never happens. You finally decide to sell it on Craigslist.
Since you know it's been used only once, and it's been properly stored for a year, you reason that it's still worth close to what you paid for it, so you list it for $3,800-almost 10% off of the new price. How is this going to turn out?