I am currently shopping for a used recumbent. I have started to wonder about fair prices for used bikes, aside from "charge whatever the market will bear".
For example, a bike ($2500 retail) with lots of nice upgrades I was eyeing just sold for $1200 on ebay. I've found a Craig's List ad for a 4-year old used bike for $1200 that sells for $1350 new. The former went really cheap, the latter is really overpriced.
Here's the main question: how should one value a bike? What's the depreciation purely on age, if the bike hasn't been ridden much? Are upgraded components worth anything like what they cost in the resale (I'd suspect not)? I think these things are a little tougher to judge in recumbent-land since the sales volume is so low it's hard to make comparisons.