I'll preface this by saying, ANY charitable work is good, any time a person can help a less fortunate person it's a good thing. It's at the basis of my argument, so many people need this charity while you have this group of people that's hoarding amounts of wealth that could improve the lives of millions of people. Maybe if all the billionaires had paid their faire share of taxes, many of these charities wouldn't be necessary in the first place. I do admire Bill Gates & Warren Buffet for what they've done, they've literally saved thousands and thousands of lives. If only more billionaires did more than just sign giving pledges.
I'll make a few assumptions for your friend:
I'll take the term multi Billionaire as having ~$4B, you say they give 10's of millions a year in charity? Lets say we do $30M, that's about 0.8% of their net worth, probably less than what they make on interest on their investments in that same year. That $30M in charitable donations is like a person with a net worth of $1,000,000 giving away $8,000/year to charity (while also benefiting from a tax write-off.) A little bit less impressive put under that perspective no?
The wealth he currently has is enough to sustain a lavish lifestyle to the next 10+ generations of his descendants without any of them ever having to lift a finger. If you know him, what would he be missing out on with a net worth of $500M that he wouldn't have to worry about with $4B? Are all the hospitals in his city world class facilities? Are none of the public school classrooms in his city overcrowded?
Pretty good idea actually.
Did you know the top 20 Canadian billionaires increased their net worth by $37 Billion during the pandemic?
Canada’s top billionaires are $37 billion richer since start of the pandemic, CCPA report finds
According to the article/report, about 1,9M Canadians are under or unemployed due to the pandemic. If all 1,9M of them got $2,000/month of CERB over the past 10 months, then that adds up to ~$38B. Literally the amount of money these 20 Billionaires INCREASED their net worth while these nearly 2M Canadians were unemployed. Now imagine with we combined that amount with what was already given, with $4k/month to stay home, we'd be over this in 6 months.
All that would still have left them with $141B collectively, literally zero would have changed in their lives.