First I just want to point out that there are many different levels of being rich. I know PG said this in one of his essays somewhere, and I have said it on this forum too. And it is true. I know this isn't what you were asking in reply, but there are certainly different levels above Level 7 (in my original scheme) that are just higher levels of monetary attainment. And that is what motivates some people to go from say Level 7 to Level 7a, i.e. they see 1M vs 10M vs 50M or whatever as different levels.
But if I understand your reply correctly, I think you are saying, what is beyond all those monetary levels? That is, assume you reach a monetary level that is enough for you financially, what is beyond that? (This is why I just stopped at Level 7 in my scheme btw.)
Having achieved some degree of Level 7 myself, all I can say is that startups are what I like to do (at least for now). I want to start all over again and climb up the Levels because each level is rewarding to me its own right. A different project brings different users and solving different needs, and I guess I just like that. So in this scheme, I guess I think of it sort of as a reset for myself; not a circle exactly, but a new path.
Other things beyond Level 7 are charity, prestige/celebrity, and doing things with bigger impact. Steve Jobs is obviously a celebrity, and I would assume he sees that as part of his success. PG seems to be in the bigger things category, hoping that YC will really change the world in a big way. Maybe he can jump in here and speak for himself though. I remember an article on here a while back (but can't find it right now) about what people do after exit events. It had these categories, but it was a little more thought out, if I recall correctly. Maybe someone can provide that link.