If someone stole an item worth, let us say $100, and the value of that item drops to say $50, does he have to return the original value or the current value?
If he returns the item itself, the question would be, does he return the item plus $50 to compensate for the loss in value from when he stole it, or does he simply return the item, because that is what he stole, irrespective of its current value?
The answer is that, provided he is not responsible for its loss in value, but rather market conditions are what brought about the change in value, then he only returns the item itself. However, if he returns the monetary value of the item, then he must repay the value of the item as it was at the time he stole it.
(See Sh. 'A., Hoshen Mishpat, Siman, Sheen Nun Dahl, Se'if Geemal, Sheen Simmakh Beh, Seif Yod Aleph, Sheen Simmakh Geemal, Se'if Aleph)
