Yah, I always wonder how do you put a price to an art piece? If it is craft item (e.g. jewellery), maybe we can cost in the raw materials and the hours spent to make it plus a creativity charge factor. But art like painting is different. A father once tried to promote her daughter's art to me and she was still in university. I met her and we chatted and I bought a piece of art from her for about 25 euros but I wasn't sure if it was a good price for both of us. But as a start, I guess it is a boost that someone bought her painting?