But of course that money could have been spent on other things, it even seems suboptimal for Bezos, which implies to me he must have so much money he doesn't actually know what to do with it.

But even worse, the 500M to dismantle part of bridge evidently isn't considered in cost of superyacht so there is a loss of 500M from city's budget because of the money because building superyacht is worth more than this loss to city - but you can see how that is a worse deal for Rotterdam then if Bezos had superyacht built without needing to dismantle bridge.