Is someone who has $100k reasonable for wanting $1M? Sure, one would struggle to buy a nice house with only $100k. With $1M it is much easier.

Do you think someone who has only $100, whose only thought is how to pay for their next meal or rent check, might similarly wonder “what difference is there between $100k and $1M? They’re both very rich!”

Point is, ambition is like a gas, it tends to expand to the volume of its container. With $400M you have enough for your own and your family’s comfort forever. With $4B it’s less about lifestyle and more about shaping the world to your liking. You might not care about that if that’s 1000x away from where you are right now, but if it’s just 10x away, it becomes more tempting.