Stipends in grad school are.... modest (see above) and don't allow the kind of lifestyle that you can maintain with a "real" job. You're still a trainee in grad school, hence all of the comics pertaining to eating ramen noodles and the obsession with free food in PhD Comics, and other blogs about grad school... (and if you didn't think you could live on this kind of stipend [barring personal or family emergencies], why did you sign up for this?)
This past week, the Professor Is In blog began a survey of PhD debt to assess whether reports she'd heard about credit card and loan debt in the 100s of thousands of dollars could be real (i.e., >$260,000 in debt for a philosophy degree). Slate Magazine, The Atlantic, and The Chronicle of Higher Education all have articles about this survey too. You can go to the results of this survey through the above link, but here's a 2012 summary from a similar NSF survey:
Over 60% of the respondents reported zero debt, but nearly a quarter reported debt over $30,000. You can enter numbers for your own grad school experience at the Professor Is In blog. Post-grad school debt is much less of a problem for students in the physical sciences and engineering probably because most of those students are offered both a stipend and full tuition when they're admitted, and because those students spend only ~5 years on average in grad school.
As an undergraduate, I went to a local state university and my parents paid for my tuition. As a graduate student at a big research university, I was single and childless, drove a 15-year-old car, shared an apartment in a less expensive neighborhood that was a bit of a drive from campus, ate a lot of pasta, and didn't eat out much. I had a teaching assistantship for $12,000 (for 9 months) and my tuition was covered by the university. I graduated with $0 debt and had a blast in grad school (and I never took a loan, never had any credit card debt, and never worked another job apart from being a grad student). So zero debt is absolutely possible.... you just have to live like a student.
I really don't understand students that complain about being broke yet buy lunch out daily, drink Perrier instead of drinking out of the free water cooler that the department keeps, buy organic berries from Whole Foods (aka "whole paycheck"), get regular facials, or drive a new car. These examples are based on real people and they are what I consider pretty outrageous choices for someone in school. If you're in grad school in the physical sciences and you're accumulating serious debt, you're making some seriously poor lifestyle choices, or you made some bad decisions en route to grad school (perhaps a you got a philosophy/religion/english degree at an expensive, small liberal arts college back east and piled up debt?). As a grad student, you're still a trainee (you don't have a degree yet!) and can't expect the same standard of living that your roommate(s) who got a job at Google straight out of college might have. But consider, your roommates may make a whole lot more than a typical grad student, but they have regular work hours, might have a dress code, get only two weeks of vacation per year (and can't leave for an awesome backpacking trip to Chile for 3 weeks at the drop of a hat [without getting fired]), and have to regularly meet deadlines (with complete, quality work...gasp!).
If you're thinking about grad school, go read the "Why did you take out the loans" comments in the PhD debt survey, think about what living like a grad student means, and consider if grad school is right for you before diving in...
