Excellent topic and I understand how this can be puzzling.
I have always held the idea that on used firearms with a price tag of 1K or more, the first 10% off should be easily negotiated. ie $,1695 becomes $1,500.
What I have always been amazed at is when a prospective buyer tells the seller everything thats wrong with his gun.....I usually consider this a buying signal.
FWIW sometimes a gentle qualifier, "would you like to open your safe and see this in there?" should preceed price negotiations.
Excellent topic, better discussed than typed.