Planning for Getting PhD in the USA

[Stanislav]

I understand. I get it that people who are sufficiently determines share rooms in houses, eat ramen, borrow from family members, and make it work. I wasn't saying, "One cannot do it because of the finances," I was saying, "If one does this, the finances may be a challenge to overcome."

True. These challenges sure look different from a low-income country.
Besides, what you are missing here is an American PhD can be one's only choice. There are only so many ways one can immigrate to the United States, for example. Also, suppose you want to be a scientist and hail from Ukraine or Indonesia. It is very possible there are about zero places in your country where that's possible. Strictly zero, if you want to make a career at it. If you're young, want to have a life in science, and do not have certain connections in shrinking domestic science world, sooner or later you move elsewhere. Sooner makes it easier, and grad school is the first stop where they pay you. I have inordinate number of acquaintances who walked this path. One guy I knew (barely) in school is Andrii Norets; he's at Brown University now and is in "Top 10 Ukrainian Economists" list. Not a single person on that list got a PhD in Ukraine. My close friend's father actually heads a big research institute in Kyiv, rather important guy. Well, his son went to grad school in Tampa anyway.
Me, I simply wanted better life and grew sick of coding (rather quickly I might add). I'm a late bloomer, actually; my sister went to US on athletic scholarship before turning 16. Our parents were relatively impoverished educators, no borrowing money from them.