Just saw this linked on Ken Rockwell's site. Apparently somebody found 65 lost negatives made by Ansel Adams, arguably one of the most influential landscape photographers. He bought the boxes for $45 and apparently they are worth near $200 mills but more importantly they provide a record of Adams' artistic development (sorry for the pun) in that era. This also reminds me of a very interesting video I saw recently where you can see Adams at work in his darkroom. A lot of his images were made to shine in the darkroom from the rough (raw) negative.
EDIT: an interesting footnote is placed on this number on the excellent "online photographer" website. Apparently the veracity of the claims is not widely accepted and we are dealing with an echo chamber effect here mostly caused by the $200M number that might have been pulled out of thin air (to use a more polite term than the author of the post linked to).