You can always offer them less. The worst thing they can do is say no. Well, they could do worse, but probably won't.

I usually try to phrase my offer something like, "You know, I realize the gun is probably worth the $350 you are asking, but my washing machine just conkedout and I have to buy a new one.All I can do right now on a gunis $250." Or something else like that, which by the way, is a fact for me right now. [:@]

That way, there is really no disputing the "worth" of the gun. They either take the offer or they don't. Later, you might then find a way to come up with the rest of the money if you so chose.