Had this happen with a couple vendors, having them decline adds negative attitude. I dunno what the scales are for if the vendor won't agree in the first place.

Noticed that its usually one weapon that he/she won't sell, perhaps this is a weapon that has been flagged as equipped?

For Arthu it was a nice staff (diff stats in each game, but in each game there was one staff he would not sell at any price). For Esmerelda it was a sweet mace, again everything else was purchaseable at normal prices, it just seemed like one item was not.

I did notice that the price seemed to be very good for the item in question, so perhaps this is a text error between suggested asking price and actual price?