Wow, reading all those replies got me so confused I actually had to rethink this from scratch. So here's my analysis:
Suppose that before the woman came to the shopkeeper, he had Rs.2000 in his pocket and an item worth Rs.200. So in total he had assets worth Rs.2200. After the fraud, he lost that item, but retained Rs.200 of the cash and he'll have to pay Rs.1000 back to the other shopkeeper. So at the end of the day he'll have Rs.1200 with him, and he'll have lost that that item. Hence, TOTAL LOSS = 1,000.
WHY EVERYONE WHO'S SAYING 1,800 OR 2,000 IS WRONG:
You're counting the Rs.800 he lost to the woman twice. When he had the money broken and gave the change to the girl, he actually just transferred his loss to the other shopkeeper and later on that other shopkeeper came back merely to reclaim his original amount. Here's another way to view it: if the shopkeeper did lose 1.8k or 2k, then obviously the other two parties involved (the girl and the other shopkeeper) must have gained a total of 1.8k or 2k (because obviously the money the shopkeeper lost didn't disappear into thin air). However, the fraud girl only gained Rs.800 in cash, and an item worth Rs.200, whereas the other shopkeeper didn't gain or lose anything, he just reclaimed his original amount.
So if you use the money gained = money lost logic, you'll also arrive at the solution that the shopkeeper just lost Rs.1000
I hope everyone understands this now.