One measure of the income gap in Jakarta is the fact that money from the ATM is so hard to use on the street.
Most ATMs spit out 50,000 or 100,000 rupiah notes -- about $5 and $10, respectively. But if you want to buy fried rice on the street for 6,000, the guys selling it often won't have change. They'll typically go around to other street sellers until they find someone who can break it.
Even paying for a 20,000 rp taxi fare with a 50,000 can be difficult. And the 100k bills! They're practically useless outside expensive hotels, restaurants and malls.
There are several solutions to this problem (if having access to large denominations of money can even be called a problem -- which of course it can't). First, you can stock up at one of the rare and sought-after twenties machines. I know of only two: one near Deutsche Bank, and the other in an apartment tower where some friends used to live.
Another is to become a notorious bill-scrounger. These are the people who, after dining out with a group, shamelessly scoop up all the small bills from the kitty and replace them with 50s and 100s. This is not wrong, exactly, but it doesn't seem like good behavior either.
Another is to frequent businesses that break large bills. The busway is excellent for this purpose because they don't bat an eye if you pay for a 3500 rp ticket with a 50,000 note.
I've seen a lot of amazing things in Indonesia -- a volcanic eruption, a lake of boiling mud, a guy who drinks his own pee -- but one of my enduring memories is of watching a woman pay for a 2,000 rp bemo ride with a 100,000 note. She was so nonchalant! It was like watching someone do a perfect triple back flip off the diving board in the Olympics. I wanted to hold up a little sign that said "10.0". I think she must have known the driver, though.