I mentioned this auction at work and one of the guys who ebays quite a bit said empty boxes can be quite sought after, and not just by collectors. They can be resued to repackage two types of items-
Final sale items you bought really cheap but cannot be returned or exchanged, often they are sold without packaging to prevent returns.
Stolen items.
You slap them in a box and you can advertise it as new and get a higher price.