- A chunk of your money will go towards a Stanford-subsidized dorm room or apartment
- Even beyond housing, the cost of living around here is not cheap
- You may not love Stanford's student health plan, in which case if you're over 26 (and can't be on a parent's plan), you're looking at paying for your own health insurance via the ACA market or otherwise
- To be making the full $64,110, you need to have advanced to candidacy (generally this is 3rd-year students and later) and stay for the summer with a "full-time" [90%] RAship. Many students do summer internships in the industry instead, in which case you're probably making way more money.
- Even with recent economic pressures, this is still much less than you can probably make in the industry, and for some subareas of CS, much much less.
I think the summary would be that if you're in a place where you have the luxury of mostly just needing to support yourself, and your health needs are well-met by a student health plan, you can afford to get a PhD here and focus 100% on it and enjoy a reasonable "student+" lifestyle for the 6ish years that will take. (Or a better lifestyle if you take summers to intern in the industry.) There's still a huge opportunity cost. The people for whom this doesn't work are often people with families to support (e.g. children and/or a partner without their own source of income) or other demands on their time or finances.
(I took two tries to get a PhD, but the second time was great!)