I think you're getting too tangled up in the specific framing device the article uses. There's no easy way for Jeff Bezos to conjure up $40B in cash to hand out as bonuses, but there are plenty of ways he could have not made that $40B in the first place.

For a dramatic example, Amazon could decide tomorrow to give the entire company a 20% raise and eat the stock price crash. They'd be fine. Jeff Bezos is prioritizing growth and shareholder value but it's entirely within his powers to prioritize other things, like paying his employees a living wage all the way down the pay scale. Amazon would be a slightly smaller and less important company with a somewhat lower share price and the world would be a better place.

When he says that he doesn't have anything other than space exploration to spend his money on what he means, in part, is there's nothing he can change without negatively impacting the metrics he cares about. The point of this argument is that he could choose to care about different metrics.