Healthy, Inexpensive foods

Protein

• Eggs
• Lentils
• Beans
• Cheese
• Milk
• Plain Yogurt
• Canned Fish (tuna, sardines, etc)
• Frozen edamame
• Whole roast chicken (use the leftovers wisely, boil the carcass into broth to use in soups)
• Peanut butter (use sparingly)

Treat meat as a part of the meal, rather than the main attraction.
Grains

• Rice
• Pasta (I should buy the whole grain varieties, but am not so good about that)
• Oatmeal
• Popcorn kernels (I make my popcorn in a saucepan with a little olive oil, then just season it with salt)
• wild rice

I don't eat bread very often anyway (generally too lazy to put together a sandwich, and I'm not hugely fond of toast), so I usually make my own. Occasionally I'll make soft pretzels too. That takes about an hour of time (and my full attention isn't even needed for all of that), and I end up with enough pretzels to last about a week (just store them in a giant ziplock bag in my cupboard)
Veg

• Frozen veg (I like to snack on little bowlfuls of frozen peas, corn, and lima beans during the hot summer)
• Potatoes
• Dark Leafy Greens (good in herby stews, or just sauteed w/ garlic in a little olive oil and then seasoned w/ salt, pepper, and maybe turmeric. Add a can of black beans to that, and you have dinner)
• Cabbage
• Cauliflower (it's not boring if you season it well)
• Garlic
• Peppers
• Onions
• Broccoli (I need to find more things to do with this)
• Radishes (good to snack on)
• Carrots (not baby ones)
• Turnips, Beets, etc. (I need to get better about eating these)
• Canned tomatoes (make for a good base to soups and stews)
• Celery

Other vegetables are inexpensive too, when bought in season.

Fruit

• Oranges
• Apples
• Grapes
• Bananas

Those are the ones that are inexpensive all year round. You can get a lot more variety by buying things in season, and paying attention to sales. I snack on fresh fruit, and occasionally bake it into desserts. Frozen berries are great snacks in the summer.