Rich people still kill themselves.
Of course, a base level of security helps improve life immeasurably - decent housing, food on the table, predictable income etc. But it doesn't protect you from emotions - grief, regret, anxiety, depression, health worries, difficulties with family members etc. We all face the same issues after a certain point.
A lot of happiness comes from how you choose to live each day as well. I don't earn much (a little over 20k per year) but I am happy because I exercise regularly, I do gardening, I see my friends, I speak to family daily, I get out in the sunshine every day where I can, and I have things booked in my diary that I look forward to (none of which cost much money).
I have some friends who are wealthy who must feel pretty rough on a day to day basis based on how much alcohol forms part of their routine. I share a PT with one of them and he consistently skips his sessions. He works very long hours in a stressful job. He may have much more money than me but I'd choose my life over their's any day.