I'm trying to ponder all this, and nothing seems to square up if I took a seller's point of view. Let me explain (to be fair, this only really applies to new, retail firearms. Used firearms are pretty fair game for negotiations):
Option 1) You see a lower price at the table yonder, so you want to haggle the price at the table you're at. If I was the seller, I'd be a bit puzzled. Why not buy the gun at the other table?
Option 2) You want to use the power of cash (vs credit) to reduce your price. Sure, as a seller, I could trim the CC fees I'd likely have built into my merchandise, but most gun sellers run at very low margins on firearms themselves (so I'm told).
Option 3) You see that the price is significantly higher than what you know is a reasonable price for a firearm, and it's the only version available at the gun show, so you want to haggle it down. Again, as a seller, I'm listening to a guy try to knock off all my profit margin and haggle as I watch 10, 20, 30 or more people that might buy at my asking price walk by, because I can only negotiate with one person at a time. Why do I consider this desirable?
This comes off as rather negative, so let's not ignore the fact that you might have purchased from me before, or you want to buy multiple items, etc. I'm just saying, overall, haggling on a new firearm seems like a waste of everybody's time. If you're an educated buyer, you already know what a fair price is for a firearm.
(Boy, if I ever start my own FFL business, this post is probably going to come back and haunt me

All humor aside though, if I was selling guns, I'd be more interested in winning customers that want to keep buying goods from me. A gun show seems like a rather poor way of winning customers hearts and minds, because it immediately sets you up in a "lowest price wins" race, and removes the ability to genuinely make long-term customers)
I don't fear guns; I fear voters and politicians that fear guns.