As a way of stimulating conversation around how much is enough…
…how about a Lotto where you choose the size of the first division prize.
This already exists in Australia, where at the Lotto outlets you can join a syndicate, and you will split all prizes between 5 or 10 or 20 people. So if you think winning $100M would be daft, you can share a ticket with 19 others, and the most you can win is $5M.
There is likely a way of doing this mathematically, without the need of syndicates. Actually, it need not be complicated at all. You simply buy fractions of a ticket for fractions of the price. Same odds of winning, just the outlay and prizes are fractions of what is nominated.
If you did win a major prize, the portion of that which you do not receive, simply goes into the next pool.
The beauty of this is that it can be announced. Someone in Sydney won first division, but chose to only win 10% of the prize. Such news could further the debate, especially if they were interviewed.
Unless you have an entrepreneurial or political idea that needs funding (me, to both), nobody has any use for $100M.