How much money is enough?

According to Oxfam, the 80 richest people on the planet now (2015) have more wealth than the combined wealth of the poorest 50% (3.500.000.000 people).  Looking at the numbers it make me wonder if there exist some kind of logic to how much money you need to have before you, if ever, feel it is enough? 

Source BBC: Richest 1% to own more than rest of world

Drawing and text by Frits Ahlefeldt, HikingArtist