dknguyen said:You can't include that $100 between the two stores as a loss because they both exchanged equal amounts of money. So he didn't lose that $100. What he did do was take the broken up $100 he got from the other store (which he paid back for later) and give most of it to the boy. The kid was the only one gaining anything in this scenario, and the kid certainly didn't gain $200 so the shopkeeper couldn't have lost it.
That would only work, if the shopkeeper passes the bogus $100 off (which he had to buy back from the neighbor). So yeah, if the shopkeeper rips off somebody else. in a similar fashion, he would loose nothing, unless he gets caught ("Honest, I didn't know it was fake...").