Cheapest foods per calorie (healthy)

I think most bulk grains/fruits/vegetables are pretty cheap. I get bulk salad greens, brown rice, oats and quinoa and they are all very inexpensive. As for foods that fill you up (help you reach your calorie goal), a couple tbs of almonds or almond butter, half and avocado, etc. - go for a food that is nutritionally and calorically dense. While they may not be as inexpensive, you eat less of them, so for me it evens out. Lentils are a great one, too!

Anything Perishable is gonna cost you! Produce, Meats, Veggies, Fruit even Eggs have gotten out of hand especially if your thowin yolks away. SO...look for Bulk sales and stock up n freeze.

Not necessarily. Esepciay if you have an Asian or Latino grocery store nearby-- their produce is really inexpensive.

Your username makes me nervous.

Especially this time of year.

you hidin' sumpin? lol

What about polenta for that (cornmeal)? It's really cheap, lasts a long time, and can be covered with all kinds of sauces. I found some great cornmeal and apple muffin recipes that are sweetened with applesauce (also not particularly expensive to make on your own).

If I understand correctly what you're after is calorie dense foods (within a budget)?

There's some really good suggestions above, a few more...
seasame oil - great for stir frys (cheap at chinese/japanese supermarkets)
coconut oil - online is cheapest

If you can (know you're allergic to peanuts) eat pistachios & almonds, they're a good top up and relatively high protein. Walnuts aren't as high but still good for you and AWESOME mixed with a little honey.

For protein shakes / bars, buy online. The bars can go a good way to eating back the exercise calories, but check the labels as a lot of them will be dairy based.

I'm very much finding that the easiest way for me to not have a huge deficit is to plan more into each meal, i.e.
brekkie oatmeal - switch water for soya/oatley/rice milk and add a banana & blueberries (go for dried / frozen for cheaper options)
salads - add real olive oil + cider / balsamic / sherry vinegar (get the oil from a cash & carry) & double the protein (i.e whole tin of tuna instead of half, or add eggs) or add nuts/seeds

Cabbage.... cook in oven with tomato sauce and pepper. Not high in calories but the fibre fills you up completely. Add ground turkey in it for extra . You will be suprised how filling it is. I shred it so that its almost like eating a pasta. delish

Look around your area and see if there's an Asian grocery somewhere. I find the best prices there on large quantities of raw almonds, long grain brown rice, and spices. For example, for the price of a tiny plastic shaker of Turmuric in a regular grocery store I can buy nearly a pound of it at the Asian grocery.

I think that your ideas are great, and if you want to keep the lower calorie fresh veggies cheaper, adding oil is a great way to do it. I can have a serving of fresh green beans or asparagus for only 20 calories but add 1 T of oil and you've added 120 calories for very cheap. You can get a 3 L of olive oil at Sam's club for about $15, which comes out to about $.63 per 1000 calories. If you went with a cheaper oil, you could probably get your 1000 calories for half that price. Over the course of the day, you could use 3 T of oil fairly easily without making your food too "greasy". Use 1 t to cook your omelette in the morning, drizzle 1 T over your salad at lunch, when you have meat, add oil, use it to cook your veggies, etc. I've even known people who've added "flavorless" oils to smoothies and oatmeal. That would add 300-400 calories to your day easily and for only about $.25-.35.

I also like to use cheese. I can buy a 2.5 lb block of sharp cheddar at Sam's club for about $6. That means that it's actually about $1.25 per 1000 calories, but when you add it to dishes, it's fairly cheap and very flavorful. If you add an ounce or two of cheese throughout your day, you've added another 200 calories for about $.25.