[jpttsn]

It's much simpler:

The point of being rich is to have all the good stuff.

To get there, it helps if you're not too easily satisfied.

Alas, many rich people go overboard on not being satisfied. When they get all the good stuff, the have forgotten how to enjoy it.

But if you're smart about it you can make sure you enjoy stuff, and also get more stuff.

You are allowed to (gasp) enjoy your previous victories, without getting complacent. You can be happy about your yacht and also work hard to get a jet.

Unless, you know, you can't. But that's just a (common) mindset problem and I don't think you're doomed to fall in that trap.

I bet this "rich but unhappy" trope is appealing as a cope for the less fortunate. Thus it gets overplayed as a trope and people wrongly think it's universal truth rather than a cliché.