Would any dm's do this?

[MarauderX]

If there is no way to sell items, and they find something that they cannot use, or have no use for, then what do they do with it? Magic that is useless is worse then worthless

There are plenty of things to do with your old magic items besides sell them. I don't have that many magic items IMC, so magic is usually a prized thing to own. The demand is always there but the number of items is never great enough to necessitate a magic item shop.
A few ideas: donate them to a church/cult of your cause, give them to a cohort, present them as gifts to a king, bribe your way to get something else, bury it in a dungeon then drop a map in the hands of your greedy adventurering competition, give it to someone you want to keep tabs on and look them up later using locate object, use it as a decoy for a thief to steal your back-up instead of your better item, sell it to the head of the guard or one of his cronies, sell it to a rich merchant, hold a public/private auction, or keep it in case your current item breaks, is stolen, burned in an acidic death of the PC, whatever.

 

[Nifft]

This item is coolness in a can! Consider it swiped. IMHO, The Box will be a minor artifact.

-- N