<< This is probably the argument that some people have been using to justify these actions.
While I would not call this thievery, it is obvious that this person is preventing CompUSA from making a profit out of this product. >>
Explain.
If they sold him the drive for $100, then didn't they stop themselves from making profit on the object (or more specifically, reducing their profit on the item by $200)?
If he gives them back a sellable drive for $300, and they sell it for $300, he hasn't cost them a dime. He made $200 on an earlier transaction which was legal.