I've been to many AIPAD shows and have seen at least a dozen Moonrises printed by Adams. Not one of them was identical to any of the others. Size, contrast, tonality of the sky (the gamut from light grey to pitch black). There was something different about each one. He certainly interpreted it many different ways over the years. With that many different Moonrises, the great disparity in price doesn't surprise me in the least.
It never ceases to amaze me how a photograph like that one can command 100s of K$ while truly breathtaking work by the likes of Frederick Sommer or Aaron Siskind goes a beggin'. Although, at this year's AIPAD show the prices on Sommer's work were quite elevated over years past. $30-$50K. However, none of them was tagged as having been sold.