I find most folks use GB to set their "private party" pricing. Armslist used to a good place to get stuff. However, in recent years they started charging $5 to $7 per month to be able to sell there. Drove most of the "private party" sellers off their board.
My advice is to shop around and be willing to pass on a lot of guns. When I find a over-priced local seller, I usually just pass. Not worth driving there and trying to haggle.
Larry