If I was a wealthy person and the calculation was based on share of wealth donated, I’m pretty sure I’d find a way to become a massive employer of temporary labor locally at $100/hr but only for 8 hours, make clear my preference for the art museum or other causes, and that I like to learn about what causes matter to them.
Accordingly, those local workers for whom I like their cause and story of why it matters to them, I’ll match their donations (based on receipts showing their donations) and also setup a series of follow-up paid interviews in the future to learn about their on-going donations to a cause they obviously care so deeply about. They keep about half the money to compensate for their time and to grow their wealth, I get to socialize with some people who support the same causes I do, I no longer have an outsized donation in my name [we wouldn’t want me to have an outsized influence], and together, we can really do great things!