I have a theory about this, actually. How it works is: people get paid at the beginning of the month, and then pay their essential bills, food, rent, electricity, insurance, Internet, etc. What happens next is, people have a certain standard of living that they think they're supposed to have, based somewhat on how much money they make, but much more on what all their friends are spending money on. They then go out and buy stuff like fancy dinners and a house in the suburbs and what not, and this spending is not mentally available as something that can be cut back on, because they don't see it as "spending", so much as "things I need to do to maintain my standard of living"; people see it as a much larger burden to write a single check for $2,000 than to spend $7 every day on coffee, because they come out of different mental pools. Anything left over after that gets put into cryonics, or existential risk, or savings, or investments, etc. That's why you see so many more millionaire plumbers than millionaire attorneys, because the attorney has a higher standard of living, and so has less money left over to save.