Another financial variable, both long-term & for an interim period of time, if one works first before starting graduate school, is the decease in income when switching from full-time employment to living on a PhD stipend. Not only will that affect one’s retirement savings, but one’s quality of life.
One’s gross full-time income, if doing some form of computational work, like coding, could easily be at least 3x that of a graduate student stipend. Plus, possibly losing employer contribution to a 401k or 403b plan.