it's a non-answer because he doesn't describe the benefits of being a billionaire. Only the benefits of being above middle class.

It would have appeared crass of him to say, 'yeah i love living in a $200 million 66,000 sq ft mansion and having the world's biggest foundation named after me. Having a such a legacy produces genuine happiness.' But he played the false modesty card.

I think his point was that a $200 million home doesn't actually buy you all that much more happiness than a $20 million home. Well, apart from the trampoline room that he seems very fond of.