How much LOSS did the shopkeeper face?

Nothing like a good puzzle to yank people out of the post-lunch slumber. One of the colleagues had emailed the following puzzle:

A lady buys goods worth Rs.200 from a shop. (shopkeeper is selling the goods with zero profit). The lady gives him Rs.1000 note. The shopkeeper gets the change from the next shop and keeps Rs.200 for himself and returns Rs.800 to the lady. Later the shopkeeper of the next shop comes with the Rs.1000 note saying “duplicate” and takes his money back.

How much LOSS did the shopkeeper face?

My first calculation was 1200. - 1000 that the shopkeeper had to give back + 200 that the shopkeeper lost on this transaction. The colleague who had emailed it said the correct answer was 1000. She explained the answer using concept of assets (the same can be found on internet). I didn't buy that. When I told her my logic, she pointed out that the 200 that he received was real money. So the real answer is indeed 1000.

As I write this, people around me are still tying themselves up in knots over this because some of them think that the answer is 1800. A fierce debate is going on – accompanied by role plays in groups.

I guess none of us is equipped to run a shop. And if we ever end up doing it, we should stick to credit cards :-)