Why can't stores just return the units?

[Zaphod]

The only exception to this that I know of is Wal-Mart and Best Buy. Due to their overwhelming buying power, Wal-Mart they typically doesn't have to pay for anything until it is swiped at the cash register.

As far as Best Buy they don't have to pay anything until the stock is in their possession for more than 30 days. At that time they have to pay. That is why they only stock a couple of this or a couple of that and they are constantly out of stock. It is because they only want to stock what they can move within those 30 days. I'm not sure if this is a store policy where they have to pay corporate for the stock they have in inventory, or if this is corporate having to pay their distributor.