Batman also doesn't fight just in Gotham, dude pays for the JLA and a bit of his family's operations, quite a few of which also have teams, and he has material for Gods, Aliens, Demons and so forth that are real issues in DC Earth and will gladly conquer or kill all of humanity, and Batman's stealth and tactics many times helped save the world...not exactly punching the villains but his other skills and gadgets.
People forget that while his main focus is Gotham, Batman is also part of superhero teams and fights in other cities or countries.
Hell, he literally pays other heroes their entire lives, for example, he owns the Daily Planet, he is the one who gives Clark Kent and Lois Lane their salaries...he is even the landlord of some apartments and houses heroes live in so he can excuse their rents when they aren't on the planet or can't pay because they were busy saving lives. now should he give all his money to Gotham...ordinarily i would say yes, but it's DC Earth, fighting aliens and demons is genuinely more important, because, great, Gotham gets to live 5 minutes without poverty before a demon destroys it because Bruce Wayne just didn't have gadgets to sneak and steal a magical item or distract the demon long enough for his teammates to save the world, that's kinda the issue with bringing real life issues to DC and Marvel comic book Earths...THEY AREN'T US, they have different issues too.