Crime doesn't pay. And in the Joker's case, that is oddly true. He's not trying to rob a bank or embezzle money or be the richest bozo in Gotham. Thinking he's an artist, Joker wants to cause mayhem in Gotham, and he spends money to do it, like when he dumps cash on the streets to lure its citizens out so he can gas them.
Joker isn't into crime for profit. He's into it for the sheer joy it brings him. See the smile on his face? Wait…if he's not in it for the money, maybe he is an artist after all…
Questions About Criminality
Why do some people wonder if Batman is a criminal? Does Batman commit crimes?
Joker says he's not a murderer, but an artist. Is there art in criminality? Can a criminal act be art?
What is in it for the police officers, like Lt. Eckhardt, who work with Carl Grissom?
Chew on This
You have to think like a criminal to catch a criminal. Batman must have a criminal mindset to be effective, so he patrols the city at night, lurking in the shadows like the criminals do.
Joker turns crime on its head. He commits crimes in broad daylight and crimes that seem to have no real benefit for him whatsoever. His differences from the common criminal element make him a challenge to Batman.