In general you can leave your money in the stock market and take out 4% a year and expect that to continue forever. Obviously there is no guarantee on that but it has held true for 60+ years. If your expenses are 40k/year you only need 1M to retire. 20M would get you 800k/year.
There are a lot of people in the world who make $18/hour. This would cover their expenses. On the other hand someone like Bill Gates or Jeffrey Bezos have much higher expenses to you.