I'm currently eating primal on a grad school budget - so it's possible. Unfortunately, grass-fed beef is currently unattainable, but you have to understand that even Publix-attained meat and veggies are better than a SAD diet so don't get discouraged.
I agree with the eggs suggestions and canned sardines (in water). I often cook dinner in large enough portions to have 2-meals worth of leftovers so that I can easily take it to my office for lunch. I've recently discovered that 3 lbs of ground chuck ($11) got me 7 meals. It may take a bit to figure out what works best for you and what the grocery situation is exactly (if you can have a friend with a car or would like to incorporate the walks to the grocery store as a regular form of slow-movement) to see what you need to buy. For me, going once a week has been working well because I end up using all of my food. When I used to try to buy for 2+ weeks, a lot of veggies would go bad and then I wouldn't have a lot to eat at the end, which would make eating out more tempting. Seasonal veggies on sale are great! I spend about $50 a week now. My cheat meals are usually on occasions where there is free food.
My biggest piece of advice would be to ignore the dietary habits of other grad students. Make eating healthy a priority and there will be room in your budget for the necessities. From my experience, a lot of other grad students buy things because "it's cheap" which includes a whole pizza for dinner because they had a coupon. And they drink a lot of beer. However, I'm not sure how this relates to your field.
EDIT: $200 a month on food allows me to eat meat and veggies, I don't eat rice or potatoes but that's a personal choice. If you need more carbs or don't have negative reactions to the food - even better for your budget.
"It is never too late to be what you might have been" - George Eliot
12 week health challenge (95%, more moving)
Start -- March 1st -- 173.4
End -- May 24th -- 158.6