Long ago that people that have millions now also had 400k and thought they never would get so much money. but then they maybe bought a shop for the monye and the made money in the shop and they started to do jobs and maybe they found a item that they had alot of and sold it to someone that give good money for it.
If you want money,
One tip. Some people wanna buy stuff from you like iron blocks if you have a iron golem spawner you can make much on that.
You can do /sell (item) and you can see what ppl who buy it from you want whobuy it for the most money.
and you can also see how far away the person is selling it.
/kurby25