A customer buys a toy for $30 (which cost the shopkeeper $20 to stock). The customer pays with a $100 bill. Having no change, the shopkeeper swaps the $100 with a neighbor for smaller bills, then gives the customer $70 change. Later, the neighbor discovers the $100 bill was fake, and the shopkeeper has to pay the neighbor back with $100 in real money. How much did the shopkeeper lose in total?