I have a theory of suicide, don't know what actual psychiatry says about it. But it seems to me that some patterns in suicide that defy simple notions of privilege may be explained by impossible expectations.
White Americans kill themselves more often than Black Americans, but Native Americans more than whites again. Some very rich groups (e.g. Hollywood stars and their kids) kill themselves often, but also some extremely poor groups (Indian subsistence farmers - possibly in connection to microcredit).
If I'm correct, the sexism of lower expectations may be a contributing factor why women kill themselves less than men, and the racism of low expectations has a similar effect on blacks.
Native Americans, on the other hand, may be more or less as socially disadvantaged as blacks in the US (correct me if I am wrong), but grow up with romanticised notions of themselves from majority culture and (First-)nationalist idealization from their own, creating an image it's especially hard to live up to from social and economic deprivation.
Celebrities have a lot of economic and social opportunity, but also everyone knows they have it, and everyone's eyes are on them. Expectations are accordingly high.
And for the poor subsistence farmers, there's nothing like a debt letter to say "you should be doing this, why aren't you doing this?". Before, they might have starved, but at least it wouldn't be their fault. Now there's a formal legal document saying that it basically is, and the entire village is involved in pushing that lesson in (if I understand microcredit practices correctly).
You call suicide an occasionally rational reaction. I'm not sure if I agree, but it does remind me of a bug I had in a connect four program many years ago. It could look ahead four-five moves or so, but it had a poor evaluation function, so it would often find itself in situations where the opponent could force a win. When it did, it played randomly. I had forgotten to penalize an early loss over a late loss, so every move seemed equally bad to it. Maybe for some suicidal people, similarly all outcomes seem 100% unacceptable, and so suicide just becomes one random equally bad option out of many.