Do you really think so? A few years ago I was making ~40k euro a year, now making ~80k a year and my life and opinions are essentially identical, other than the fact I save slightly more and treat myself to a few more things. I would assume 180k euro (200k usd) would net me a slightly higher quality of life and an earlier retirement but otherwise not much else. Amongst my friend group incomes vary from around 12k (dole) to about 150k and apart from some people having less money for leisure (resolved usually by having a night in as opposed to a night out) it doesn't really lead to any tension.

Is this some cultural aspect I'm missing here? Eg lower social cohesion between income levels in the US?

Or maybe it's just a life stage thing. I'm still in my 20s, and none of my friends or myself have children. As time passes and savings mount and people start having families maybe the problems emerge...