Sure, the yacht is only 500 million, that also doesn't include the 75 meter support yacht he often has sailing with it. Now add in his 4 private jets (roughly $250 million total), his three mansions on an almost private island off of Miami (roughly $240 million total), his roughly $40 million into his Washington DC house, his 30,000 acre ranch, his properties in Beverly Hills and Manhattan, and more I'm probably forgetting about (I know he owns more ranch land than just that 30k acre property, it's just the most well known since it now hosts his space company). Not even counting clothes (which Bezos is known to have a pricey watch collection despite wearing a "reserved" choice usually), food, and other expenses which definitely add up. That's a solid billion right there in real things he's bought.

Sure they can't tap the full "value" of their net worth, but the more they have, the more they can tap. And it's a disgusting amount. And they absolutely treat it as cash equivalent.