Disclaimer: I'm anal about this stuff...

I tend to look at it slightly differently - the owner who kept all the various paper bits and pieces is more likely to be the type of personality who takes really good care of the equipment. I want to buy stuff from those folks because while used, it's almost never abused. Thus I'm willing to pay a premium for a gun with a matching box, more because of what it SAYS about the gun's history than for what it IS by itself....if that makes any sense.

Helped a buddy pick up a pristine used gun just the other day - owner had the original paper box endpiece (cut off the cardboard box and stored in the nice plastic hard case), all the little paper hang tags, the card-stock backers from some accessories which came in that shrink-plastic packing, etc. Needless to say the gun looked nearly new - if you didn't check internal wear points and if someone hadn't obviously "test-fired" it recently (and not cleaned after), you would have thought the gun was NIB. That's MY kinda buy!