I've heard that some universities set aside $5-10 million whenever they grant someone tenure. It's a fiscally prudent accounting measure. And it's also a measure of how valuable the contract can be. (Of course one still needs to do some work soooo....)

I wonder if that's the amount to endow a chair or something, because $5m is well within the "never work again" FIRE amount - but perhaps a tenured professor not only has his salary, but that of his assistants, etc.