Belittled when selling them their own items

Yesterday I wanted to sell items that I had bought a long time ago fro A2Z. Two Paintings that I had paid R750 for each and two butler's trays that I purchased for R 1 200 each. I wanted to sell these items back to them but the reception was not good. They offered to buy all these items for R 250.00! I would like to know how selling to this store works. With this kind of treatment, I do not think I will be buying there ever.