Yes, but only insofar as they have basic material security and more free time. Those are the most valuable things more wealth can give you. I'm pretty sure there have been studies into the effects of greater and greater sums of wealth, and past a certain point (roughly what would make a person materially safe with vacation time) more money didn't do anything for their sense of happiness. edit I see people posted the study I'm talking about in the comments already

I think the alienation under capitalism bit still applies though. It's probably not good for a person to psychologically detach themselves from the rest of humanity like that. edit Though I do wonder if a person who genuinely only cares about their personal comfort and status has an easier time being happy simply because there are fewer boxes to check? Like, if you genuinely care about the state of the world, your own personal fulfillment cannot be enough, because the state of the world as a whole matters to you deeply.

Don't dwell on this shit too much though. I can understand how upsetting it can be wondering if the shitty people are having a blast while the rest of us and our loved ones suffer. But, agonizing over finding a way that "actually, the most powerful people aren't happy, so really they lose anyway" bullshit that doesn't and shouldn't matter, is simply wasting time and working yourself up. Whether or not our class enemies enjoy or suffer a certain psychological state is irrelevant to improving our material conditions.