If there are two identical firearms side-by-side and one has a case, I'd honestly take the one without the case. I still have half a dozen factory rifle boxes and 20-30 factory pistol boxes on a shelf, but I've simply tossed the vast majority of my boxes.
An original factory box add near zero value. It's possible that to the right buyer, at the right place, at the right time, with the right firearm, the box may make the firearm more attractive. But very few people actually care, and fewer still want to store the box. They take up too much space in the safe. A possible exception is the CMP cases. For some reason people are super willing to pay top dollar for an item that comes with proof that last month the seller only paid half of what they are reselling that M1 Garand at...
