Scanmead has mentioned some very valid points, the art of creating skin texture is an intensive art, demanding hours of concentrative effort to generate, not only, image maps, but proper bump, displacement, specular, etc mapping as well.  I read somewhere that the most realistic skin is a product of actual drawing, not patches of photographic images stitched together to create a lifelike model.  Even using Luxrender, if the skin texture sucks, it will be obvious in a real sense.  But would you be willing to pay top dollar for one or two "perfect" skin textures, or accept mass produced packages with little regards to quality craftmanship.  Even BB admits that there is an extreme shortage of great skin textures present in the marketplace.