Does allowing card trading at card shows (or retail stores) promote or hinder sales?

[abothebear]

The store by me has a bid board where patrons can consign their items with the store getting a commission. It means that most of their older cards sit unsold at their becket price tag. But most of their business is fresh packs and suplies anyway and this weekly project brings in people on a very regular basis - to see what is on the bid board, and to see what they may have won, to drop off stuff to auction, and pick up the little bit of money they may have got.

I am convinced it is what keeps the store in business. And it is the main reason I got back into collecting - I checked out the store just to see what was up with the hobby these days and saw I could bid and win the cards I always wanted as a kid for a few bucks (I won a handful of '68 Topps HOFers for nothing and was hooked back into the game). And it provided a way for me to get cards for my son very cheap. I could get a box of newer cards sans patch cards for $10 and put together grab bags of 100 cards for less than a buck (with patch cards I pick up off the board of players I choose), whereas a pack of 7 cards with costs $3. And any cards I don't want clogging up my kid's room I put in another box and auction it off and get some of my money back.

I'm pretty sure they have done a trading night before, but I have not been to it. I think trading would have a similar benefit to the stores and to shows.