There may be a lot of Amiga user's out there who have an A4000 and don't have a box. It makes it a more complete unit. If I was considering buying an Amiga and there were 2 which were in comparable condition and one had the original box and one didn't, I would bid first and more money on the one with the box. But of course, that's just me. I know that in area's such as toy collecting, the original box can make the item worth many many times more than the same item without the box!
Dan