In addition to the excellent answer by Chris Han , some sellers have Minimum Advertising Price restrictions (MAP) by their distributor or manufacturer. They cannot sell items below that price without jeopardizing their relationship with the manufacturer. read more
So, sometimes they will list an item as open box, floor sample, or “used, like new” so that they can sell it without violating a MAP policy. I would certainly ask the seller what the situation is with the item before purchasing. read more
The answer is simple, they are great deals. Many buyers think of 'Open Box' items simply as returned items that a customer found defective in some way. Although, this may actually be the case in some listings, the majority of sellers that list 'Open Box' are reputable dealers that present a real bargain. read more
A B item, open box, etc. is a way to circumvent these rules. I am in Malaysia and find ebay(USA) prices to be around half of dealer prices in Malaysia. On that basis I buy a lot of B stock from USAand save a lot of money. read more