Regarding bicyclebluebook.com or whatever. Not accurate all. Feel free to reference it if you are offering a lower price on a bike. I have no idea how they come up with their pricing, because it definitely isn't associated with the prices that used bikes sell for.
About every day I search craigslist in with a 250 mile radius of CO, LA, SF, Seattle, DC (occasionally Dallas). I will say I look at the listed places because there are a good number of tandems being sold in these markets. Despite what folks are saying if there are good deals on more modern tandems in these places they go pretty quick. Bikes that are 9 speed or older with rim brakes that the owners are asking 50% of the new version don't sell. Similarly folks who are trying to sell newer bikes at 80-90% of the new MSRP don't sell either. If you're in a more rural area there probably isn't really a market so prices could be all over the place.
I'm never offended if someone low balls me...I just may not respond.