While arguably Batman could use his wealth better (especially in versions where he's richer than Luthor, because you don't get to be richest guy without being a major asshole who does things like force workers to pee in bottles), the other guy/gal also has a point. The comic book universe isn't our universe, it has aliens invading and Spwecial People who have to be fought by other special people. Batman is basically super-powered the way he can run a marathon, run a chemical analysis and synthesize a new cure for something overnight, and jump 10 feet, they just pretend otherwise.
You might enjoy Harley Quinn where Batman gets arrested for tax fraud.