Photography and Art Market

The main aim of my Master diploma work will be an?? effort to describe the Art Market and especially the position of photography into it. When photography began to be part of the Art Market and why? Is the entry of photography in the Art Market a reason for a change of the photographic discourse and further more is that a fact by itself which can affect the aesthetics of photography. How photography has been affected visually, thematically and even the way of the installation of the photographic image? Is it true the hypothesis which says that as bigger the size of the photograph as much bigger art it is? "Art is about life, the art market is about money." Damien Hirst said. Is that so? Or maybe nowadays art is only about money. Has art market and art become one? The above questions are some of the elements which are going to constitute the research of my diploma work