So a lot of the time you see millionaires and billionairs on shows trying to guess the cost of stuff and going majorly out with their guesses (either two high or too low or it's just an arbitrary guess). But from what I've noticed, most people don't keep track of how much money they have, how much they're spending and how much they need...
That's why those people are not millionaires. Poor spending habits are very common, people don't look for better deals, don't bargain, don't control themselves, don't invest money and then wonder why they are so broke.