Using your example, a billionaire doesn’t hand 1,000 more dollars to a hedge fund manager and get 1,000 times more wealth amplification. They hire a team of accountants and lawyers to do 1,000 times that base amplification each.
Making 100k and having a stock based retirement plan is an open drainage from the wealth factory, it definitely has access to the same levers, but it’s effectively the equivalent of a pension, just managed in the marketplace according to marketplace rules. That earning category is basically the automobile manufacturer lead/plant manager of our generation, the only difference is there’s more people who get that slice. People in this role largely don’t have the capacity to even think about increasing their leverage, they just get “benefits” and call it a night.
People who become billionaires have an entirely different approach. Their work is split between using whatever leverage they have access to, and whatever affords greater leverage. It’s mathematically the only way (given current dollar valuation) that you can get that many dollars.
(See also the sibling comment to your by pdonis.)
The term "using leverage" is often used in a creditor / debtor relationship. But it's funny how the term works because in that setting "using leverage" is usually associated with the debtor being the exploited one in the relationship.
More generally, in a given exploitive relationship it's not always obvious who is exploiting who.