I'm dealing with this scenario right now. A friend met a guy at a gun shop who was trying to sell a few guns, and the shop had no interest at all. My friend referred the guy to me as an "expert" (of sorts) and told the guy we might be interested in some of the guns. Seller has no idea of the guns' current value and doesn't even remember what he has, except for the first three pieces. Pretty ordinary guns (although one is a post-'64 Win 94), but he thinks they are golden because he bought them all new in 1968 and they are allegedly unfired in the original boxes. Doesn't sound like any of them are collectible, so I'm pulling numbers off GunBroker and GI to explain to him that none of this stuff is actually selling these days for anything near the asking prices. We'll probably try to buy a few pieces at what we think are fair prices, and the seller will reject our offer. We'll still have our cash and he'll still have the guns he wants to sell. Nobody wins, but at least he gets good info on the value of his stuff. It's up to him what he does with that info.
