Here is my thinking. If I see something at an exceptionally good price and I feel the person has priced as such because they are just not knowledgeable or fell into some misfortune, I will tell the person it is a good price and not dicker. Kind of a karma thing to me. This also may help to keep someone else seeing that amazing deal and snatching it up.
If someone has a goal of making money moving drum equipment, they most likely bought the equipment at a cheaper price so I have no problem offering a lower price. As said earlier, "just business" as that person was probably doing "just business" when negotiating the purchase price. The same thought applies if it is just an average Joe selling but the price feels high to me.
I personally do not like to play games when selling something so I will price at what I feel is more than fair, usually toward the lower side, and state the price is firm. It helps to eliminate the hurt feelings. Now if I say price is firm and someone offers me less, I do not even respond.
Wes