Buying/selling has been all over the map in my life. In some instances, I was the ignorant one for paying too much. Probably went the other way as well. I once put a unit up for sale as an auction item. I was a little embarrassed at the selling price because it was out of line for the actual valued price of the unit.
It also has happened more than once that I have sold a unit only see them resell it for sale at a much higher price elsewhere. Hmmm.
I believe that you must be comfortable with the price decided on for sale or purchase. In my experience, I am also more comfortable selling without negotiation knowing that the product has been properly priced to begin with.
In my other hobby of woodworking, and acquaintance of mine always makes sure that you know just how really expensive and impressive his new machines/tools cost.