I've lived / worked in midtown Manhattan on both $35k/year and $90k/year (and between) within the past 3 years, and they are both doable. At 30k, I wasn't rich for sure, but I wasn't poor either. Still going out to eat mostly, and not missing out much with friends.
As it got closer to 90k, things got easier for sure. I'm not married, so no dual income, but my total monthly expenses come out around 2k (rent, good food (never eating at home), utilities, misc stuff) which leaves about 3k/mo left over. I would consider this materially wealthy, at least.
> I'm not married
So having roommates was an option. And you didn't need another bedroom for the kids. Your housing costs were far below those of an average family. Which is sort of the point of all the comments about dual incomes being required.
As it got closer to 90k, things got easier for sure. I'm not married, so no dual income, but my total monthly expenses come out around 2k (rent, good food (never eating at home), utilities, misc stuff) which leaves about 3k/mo left over. I would consider this materially wealthy, at least.