Aldi is my go-to for almost all groceries. 3 pack of romaine hearts for .99, bagged spinach for 1.69, zucchini are 2 or 3 for around 1.50, cauliflower for .99, 3 peppers for 2.00, mushrooms for .99, 5 pack tomatoes for 1.50, over 1lb frozen Asian mixed vegetables for around 2.00, frozen peas, corn, and green beans for under 1.00 each.
The vegetables are truly never killing my budget. What does eat into my financial and calorie budget is meat. I stretch almost all meat by incorporating around 50% vegetables into it.
For example, 1lb of lean ground beef becomes much larger (and better for you) when you food process 1lb of mushrooms and mix it right in. Things like meatloaf are made with finely chopped onion, pepper, mushroom and spinach. Meatballs are made with shredded zucchini, chicken nuggets are made with shredded yellow squash, chicken breast is pounded and stuffed with spinach, etc.
Fast food is not that great of a deal. I buy 10lbs of potatoes for $3. If I cut and make those into fries, I will beat the price of a "value" fry at any fast food restaurant.
is a great recipe blog with cheap and delicious meals. It's not "diet" food, but most of her recipes are pretty balanced.
The ultimate thing that has saved my budget is cooking once, dividing, and freezing. 1 pot of chili = 8 individual meals to divide and put in the freezer. 1 stew = 8 more individual meals to divide and freeze. Cook one burrito filling and buy one pack of tortillas, roll, and freeze for 8 individual freezer burritos, and the list goes on.