It used to amazed me that some artworks are worth so much. It was because the work was great, I thought, therefore the price justify the work. Now, It still does but... maybe it is not that simple.
In my experience of gift giving, it is the person that makes the gift valuable, not the other way around. Perhaps It is not just about the skill nor style that made the painting valuable, but the name attached to it that made art valuable. For whom was it made? Who did it belong to? These are the questions that led to art being born. This is my guess.