We have a household income of 30k. We're happy. We have a warm home, food on the table, a very pleasant life. We get by and enjoy our lives walking, running, reading, etc.
My colleague, with a household income of circa 90k, is desperately unhappy - chiefly, and she admits, because she feels she hasn't got "enough."
She lives in a smart area surrounded by people with huge houses, Range Rovers, new clothes, "done" nails, regular salon trips, foreign holidays, nannies, endless clubs and music lessons for the kids, you name it.
Every person in her house has a tablet. We don't have one between us. She's been away four or five times in the last year, we haven't been on a plane in years. Our honeymoon was in a tent in the UK. But we're happier,I think because we're not aspiring to a "lifestyle" that involves endless stuff.
50k is a big household income. But not if you want holidays, cars, gadgets, haircuts and the rest - as well as somewhere to live, bills paid and food to eat.
So yes, while enough money helps, so many people never think they have enough. So it doesn't make them happy, it makes them more depressed because they're on the cusp of a lifestyle they can't quite afford, or at least not easily.