Well, if anything, Gotham's villains have always showed a preference for murdering rich people. Remember, it's a place where the sum of money you invest in your personal protection is totally irrelevant. And I don't know if you read the most recent Joker War, but it has been a real nightmare/warzone for its citizens. Realistically, should be thousands of refuges escaping from the city, like the poor people from Libya to Europe. It don't even make sense that any important company want to keep open a branch there. Gotham at this point is like Beiurut in the worst days of civil war. The only difference is the citizens of Gotham do not have to embark on dangerous boats that risk sinking to escape, all they have to do to save themselves is take a train (obviously if the Joker does not poison all passengers with his gas first).