Please help me understand the thoughts of people who actually want (for example) $20 Billion Dollars. Depending on where you live, wouldn't $5M be about enough?

"Poor man wanna be rich,
Rich man wanna be king,
And a king ain't satisfied,
'til he rules everything..." ~The Boss

Could you be happy (for example) in a comfortable middle-class life? In case you do not know, excess money can create related problems. Seriously, why would anyone want $20 Billion Dollars?