Frankly, I think 5 million USD should be enough for anyone pretty much anywhere in the world to live the rest of their lives comfortably. Taking 1 million out to spend immediately and leaving the rest in a savings account, even at 2% interest per year, you're getting 6666 per month, or 80k per year.
For me, personally, living in Brazil, 600k dollars would probably keep me afloat for the rest of my life with my current expenses and comfort. That's roughly twice my current salary for the next 25 years.
So, when is it fucking enough!? When will these people have enough money?
For many, it's never enough, because they see it as a competition, one about showing off "wealth" in the most cringe way possible (just look at all the assholes that love to show off their expensive car collection) and also where they interpret rules like in the Munchkin card game: it's ok to cheat, so long as you don't get caught.