In both of those cases, wouldn't the creation of those assets require burning $500M in real stuff? Gold as well as Bitcoin costs what it costs because of the expense of mining, which is real peoples' lives, materials, and fuel burned.
If Bezos kept his $500M in Amazon stock or cash or something, then it would be just numbers and not waste.
What needs be recognized is that "allowing" Bezos to do this is not an ideological or engineering question between what is optimal or suboptimal. It's a question of how much confidence do we have in our interventions. Humans naturally engage in trade and acquisitive behaviors. There have been rich and powerful men for many millenia before Adam Smith wrote Wealth of Nations and capitalism became a philosophy. Commerce is a default, not an imposition.
The question is whether armchair hot takes, politicians, bureaucrats, economists, and ideologues are qualified to make confiscatory decisions against "the wealthy" that will not do more harm than good to society as a result. Our world is a system that is too complex to understand easily, or sometimes at all. If it ain't broke, don't fix it. There isn't mass human misery resulting from this yacht, but preventing the order could lose people their jobs and have who-knows-what consequences. So maybe we should chill.
We don't live in a world that's big enough for millions of Bezos's to average out, so I think it's a fallacy to appeal to a laissez faire, free market approach. To the extent it works and seems logical, that's in the context of a huge economy with millions of people.
Bezos being the product of a (sort of) free market doesn't make his actions free-markety once he's attained his current level of power. Treating him as different from "politicians, bureaucrats, economists, and ideologues" is wrong because he's not fundamentally different.