No one is worth a billion dollars.
Because the society in which they live cultivated the necessary environment and capital for their business/idea/invention to exist and to be bought.
We a live in a society. They should be taxed heavily on the sale and excess wealth. They can be in the top 0.01% with hundreds of millions of dollars and still live like a king without billionaire status. At a certain point the wealth must return to the people and the society in which this idea was allowed to flourish. Because without the roads, the regulation, the law enforcement, the trash collecting, the teacher who taught this person, the food that was grown and delivered for them and the others who helped them and everyone who paid taxes to the society in which they live… all these people are investors in this person and their idea… and when someone creates a really big idea worth billions, in a society and environment where such an idea can develop and be bought… society should earn the dividends of their investment in this person who created this billion dollar idea.
No person is worth a billion dollars. No person got there on their own. End billionaires.