Regarding well-off people being suicidal, keep in mind that they are also only human - meaning that they could have ended their lives because someone they knew died, or any other reason at all, really.
I understand the whole discussion around being wealthy, but being wealthy doesn't automaticallly free a person from their potential other causes of suffering.
I may be missing some important element to life here, but I'm guessing that most people strive for good enough wealth, health, love and self-fulfillment, and if one or more is missing, there may simply be no point to life.
When I think about such people, I think of Tim Bergling / Avicii.