I agree with your point in general, but I think you'd need to scale the two example numbers each up by an order of magnitude. A hundred-millionaire is definitely rich, but can't buy all the houses, boats, private islands, etc. that they want. A single property or a yacht can easily cost well into the tens of millions. Plus if you're living in a $10M+ home, your annual expenses are presumably significant, so you'd want to keep a fair amount to live off of.

It's probably ridiculous to most to think of hundred-millionaires being financially constrained, but I do think there's a material difference in the buying power of $100M and $1B without getting into unique goods.