I always wonder about when there is a cutoff about the grift, i mean there has to be a point when enough is enough. Who cares if its 4 or 5 billions in the end, thats more money one could reasonably spend in a lifetime. What drives this greed?

Power. People who want power need status, and money is the ultimate symbol. They can never have enough power because of their dark triad personalities.

The idea of winning. They have to keep winning because the idea of losing threatens their identity, which is in being a winner.

If I understand Trump, he wants to be the richest man in the world. It is another matter if can achieve that. But his ego would definitely want that.