A German philosopher, cultural critic and essayist, Walter Benjamin stated in his book The Work of Art in the Age of Mechanical Reproduction (1936) that the "aura" of an artwork diminishes through mechanical reproduction. The work of art which can't be mechanically reproduced, such as painting, has greater presence of originality and authenticity.
While it is true that with photography the human "touch" was detached form the art work, for the first time, and replaced it with a machine. The concept of reproduction has always been present in the arts. The early cavemen paintings used easily duplicable figures and handprint stamps. Later on people copied the artworks of masters in order to develop their own techniques – a kind of reproduction of its own. Same goes with technological reproduction. The ancient Greece had its methods to mechanically reproduce patterns: creasing and embossing. Wood engraving made graphic art technologically reproducible and the invention of printing made the same possible for literature. Also original paintings are reproduced by printing to make them more accessible to the public.
Wood engraving then and now
Benjamin's statement is understandable: the possibility of mass reproduction of a photograph and the rapidity of the process could be seen as diminishing factors for the artworks "aura". It does not, in my opinion, concern with the uniqueness or value of the work of art. It is still the artist's "eye", the unique vision that makes the piece come into existence. When it comes to the value of the work, art photographers know and take these factors into consideration. They only make a set number of prints, the less there are the more "rare" or valuable the prints are. They can also print big or use unusual printing methods to add to the value of their works.
This photograph by German artist Andreas Gursky was sold for 4,3 million U.S dollars making it the most expensive photograph of today.