It was really difficult for me to get used to Indonesian currency.  10,000 rupiahs = about 1 USD, so all those 50,000 rupiah bills are only about $5, and they had 1000 bills, which is only about 10 cents.  The bills for the lower denominations were filthy because they were obviously used a lot.  There were coins for amounts lower than 1000, but we rarely got any.  Every time I made a transaction, I had to think a long time about how much I had to give them.  Too many zeroes, and it was confusing after getting used to thinking in terms of won (1000W = about $1).