This assumes there is any benefit at all to them 'saving' in a situation where they're drowned in money specifically because they already have all the money and seek more from people who assume money is best spent by giving it to entities who already have the most money.

Sort of 'progress through increasing the highest possible score'. In this light, spending excessively on administrators and absurd things is a form of virtue signalling meant to elicit further gifts through demonstrating they are already wealthy beyond all imagining.

That's not a joke: that's actually how it works, and there are many parallels, for instance in the stock market.