i've been told you get the best bargains just as there packing up on the last night of the fair,but i think it depends what your buying.I know the guy well that used to own Grahams gun shop in Inverness,he told me the top end brands Zeiss,Swarovski,Leica he couldnt give much of a bargain on because he hardly made anything on them.But mid range stuff he had a big mark up on so could knock a fair bit off the price.
Sound moderators have a massive mark up on them so definatly worth a haggle.