I don't think the original box adds value but to me it just sort of makes a used firearm more attractive. No real reason, I wouldn't pay extra for the box but it's always a nice bonus to have it when buying or selling a used gun. Then again, what do I know. I put all my factory boxes in the attic for safe keeping and then lost them all when my house burned in March
Most I don't care about, I do wish I had some of the older factory Colt boxes back.