OK, I've finished supper so now back to the thread...
A big part of how the dealing will turn out is how motivated the parties are to it. I'm kind of a jerk at times and I often just don't care if I sell or not. Some of my guns just travel with me. I only have them up for sale because I feel I've got to have "wares" on my table to sell. If I sell them, I've got to select some other peach from my tiny collection to put up for sale. And it won't be pretty if I want to keep it!
My gun show table pard always over prices his stuff. He does it because he knows the buyers will try to skin him. He's finally convinced me to do the same on some items. But in the negotiations I see, no matter what price you list, the guy asking (many not serious about the gun) will toss you a lowball, just to see. Back when I was flush with guns and money (before retirement), once or twice my contrary streak got the best of me and I would just accept their offer. Mostly it wasn't an offer and they turn tail and run off. Occasionally they retreat to think about it (hey, they made the offer, and it was a lowball). But if they came back, we started at the original price and not at their first offer. Once I even told such a guy to "move along".
Sometimes such a buyer gets a really good price on an item. When they leave, the seller can get an attitude. At an antique show a few years ago (its this weekend, so I'm assuming it was 2 or 3 years ago) I walked up to a silver vendor (Vi Walker out of Indy). He'd just experienced one of those situations. He had some great water "glasses" made of sterling, by a silversmith in Japan (Hirata). It was a full service of 12 of them. They had negotiated for almost an hour, but the lady and her mother just couldn't pull the trigger. I took one look and realized they were works of art, in perfect condition. When I asked the price, he smiled and said "I'll give you the benefit of the last lady's haggling". So I bought them for that amount. He finished up by saying one of his favorite things is to have an indecisive buyer come back and find the item sold.
Which brings up the idea that such negotiations don't always happen in a vacuum. Others may even overhear the dealings and wish they could buy at the suggested price. Once a potential buyer puts an item down, it becomes a different show. You can walk up and try your hand at the deal.
And in the gun show circuit, there are just conventions we kind of adhere to. Trying to get another $5 or $10 off a $500 or $5000 item will probably tell the seller he's dealing with an idiot.
I've got a really nice M12 I've been shipping around for a long time now. Its too nice a gun to just give away. I've priced it at what I think is a fair value of $450. I've had a few offers of $400, but I always return with a counter offer of $425. Its basically the bottom price (unless some other factor, like someone is a repeat buyer from me. If they don't want to pay, I don't care. I'll just lug it around until someone pays the price. It fills a spot on our empty table.
I'm not under any pressure to sell. Buyers don't know that. I'll eat tomorrow regardless. I even kind of like the gun. Its a difference from a pawn shop, where you can pretty much assume there is a pressure to sell something.
Part of negotiating, be it a gun or a car, or a piece of jewelry, is understanding what motivates the seller. It also helps to get an idea of what the cost on the item is. It won't make the seller happy, or gain you a deal if you're trying to skin him (buy from him and make him lose money.) If you want to own the item, but absolutely won't allow him any kind of profit, I predict an unhappy future for you.
Realizing you have a family to feed might make you want to fight for every cent. But he has a family, too. Once you make it clear you're trying to beat him to death, he just might harden his stance and make you pay more than you would otherwise.