Here's an example of a box that is worth as much if not more than its contents. It just walked into the local train shop as part of its train set (#2223W). The owner had no idea of its value or rarity. He was amply rewarded in the four figure price we paid for the set. You never know what's out there.
As far as box restoration is concerned, it can be approached with the same techniques as used for museum preservation of valuable paper documents. It's just a matter of matching the degree of effort to the eventual value of the item.