There is a local site that is mostly Texas Gulf Coast people I visit occasionally. It is a fishing site, but has an active buy/sell forum for guns and hunting. It isn't that much different than what you are describing. The most common overpriced stuff I remember are custom AR's made by some local gun shop with a mix of parts. The main thing is that reasonably priced firearms sell quickly and the other stuff languishes until the owner drops the price. I haven't visited Armslist much, but I am assuming it is similar.
In my experience, Pawn Shops are similar. Mostly stuff is either overpriced or crap. The occasional good deal doesn't last long.