How does one determine the value of a koi over another?

 It can seem strange to the new hobbyist that one koi can sell for $100 and another only slightly different looking koi can sell for $1000 or more.  It is difficult to sum up what makes a koi valuable, but the easiest  place to start is the koi show judging standards as these will dictate what the rest of us pay for koi.  Koi shows are not unlike dog shows.  It's a competition were the koi are viewed and judged by a group of experts.  Numerous winners are chosen including the Grand Champion.   Just like in dog shows, the judges use a very specific, even rigid, set of standards to judge the koi.  Body shape is by far the most important aspect and is worth the most points when judging the koi.  Other attributes like skin quality, color and pattern also come into play.  Each variety or type of koi also has their own set of standards for that variety.  The value of the koi is often determined by how closely the koi fits into this set of judging standards and how well the koi would do if entered into a show.  Koi that will do very well in a koi show are often referred to as "show quality koi" and these will sell for a much higher price.  But beware, not all koi marketed as "show quality" actually are.