Yes, halachos of tzedaka do mandate how much one must give. They require a wealthy person to give more than just maaser.
My objection was to the heter you and others are giving, saying taavos are fine as long as you’re not spending more than what you have. That’s factually incorrect. I don’t go over to rich people and tell them what to do, because you’re correct that it’s not my business. Taavah in general is a personal issue and middos in general are usually outside of the parameters of personal tochacha, because they vary from person to person. One person’s supper is a person’s taavah, and we can’t know.