I have heard many times that the concept of the "hashkama minyan" in America began because frum people went to work on Shabbos in order to not be fired and feed their families, and wanted to daven first. I have never heard it discussed if what they did was justified on the grounds of pikuach nefesh. This question is probably not as relevant today, given our much better economy and the prevalence of government-assistance services and Jewish tzedaka organizations that can help people who are in poverty, though I think it may still exist, as homelessness is still a big problem and not everyone has the ability to find those resources.)
In any case, is anyone aware of any teshuvos from the Great Depression or other times which deal with this question?