It's a poor analogy. Dragons take the gold from the people and kept it from them so it can't be used.
The 200 billion that Bezos is assumed to be "worth" is currently in the hands of the people, being used by us. If we wanted to fix society instead of buying amazon shares we could do it today. Bezos hasn't "hoarded" it, we have it.
"To the dismay of Thorin, Smaug the horrible turned out to sit on a pile of paper that anyone could buy if they wanted to and all the gold was already in circulation in the town of Bree."
If only there was a metaphor to explain that. Maybe something about a mythical creature, hoarding piles of treasure.