> Once you reach a certain level of wealth, your net worth increasing becomes a substitute for income because these people live of the debt backed by their illiquid assets. That allows them to avoid a large tax bill.
Income is periodic. I get a salary every year. I can spend that amount every year as long as I'm employed at the same salary. Elon Musk can't spend 220 billion every year. If you want to compare net worth to income you should look at if he were to sell his shares and put it in a safe annuity earning 4% a year or so in perpetuity. So take his wealth, and multiply it by 4%. Also note that the annuity won't grow, unlike my income.
> Take out a $1b loan using $10b in assets as collateral. When that $1b loan comes due, your net worth has grown to $15b.
So you can expect his assets to grow at 50% a year? Here's a life hack: invest in Tesla if you think its going to grow 50% a year. Then even with $100,000 invested today would have you become a billionaire in 23 years!