For some people, money is not for buying things, but just for keeping score. That can make it rewarding and addictive to accumulate money, even if you don't buy anything (like a giant house) with it.

The score keeping aspect makes it interesting, just like playing tennis while keeping score is more interesting than just hitting a ball back and forth across the net without counting.

Yeah, I kind of agree. I read Andrew Tobias's (did I get the apostrophe right?) book on investing and he made a point very early on: the people who are rich like money. No, not like you and I like money, they like money the way you and I like fishing, or reading, or hiking or whatever. It's their hobby, their love, the thing they like to learn about, read about…

Warren Buffett wouldn't be where he was if he wasn't obsessed with money. But to your point, that doesn't have to translate to material goods: the bigger house, yachts, etc.

Maybe he just likes building things that others find useful.

When I was younger I rented furniture from a company called CORT. I happened to notice on the contract or receipt or something, that it was a Berkshire company (I didn't know that before then).

If I were Warren Buffet, I would have been happy to know that someone was a satisfied customer of one of his companies. I got some decent furniture for a few months at a reasonable price.

Just like I'm happy when someone is a satisfied user of my software.