I make almost everything from scratch which saves a lot!
Make your own chicken stock by simmering a whole chicken with the end pieces and peelings of carrots, celery, and onion (I keep a bag of end pieces in the freezer that I add to whenever I peel carrots or chop an onion and use it when I'm ready to make stock).
In recipes that call for 1lb of ground beef/turkey for example, I only use 1/2lb of meat and add diced fresh mushrooms to bulk it up. Depending on the recipe, I will also use minced red bell pepper, carrots, and/or onion. I do this frequently with spaghetti, healthy sloppy joes, and Asian lettuce cups.
Rice and pasta is inexpensive, as are beans (especially dried beans). If you buy dried beans and soak them yourself, you will save a TON versus buying canned beans. We don't eat much rice or pasta, but it is a big money saver. You can even make your own "refried" beans in a crockpot.
Various soups are very inexpensive and this is the perfect time of year to whip up huge batches! I like to freeze extra for later use. I like to serve soup with sandwiches (usually just 1/2 sandwich per person as long as the soup is a balanced meal). Sometimes grilled cheese, other times BLTs.
Certain sandwiches are dirt cheap...egg salad sandwiches are one of my favorites and eggs are so cheap! We also love making teriyaki chicken sandwiches where we cook cubed chicken in teriyaki sauce, then add diced pineapple and a slice of Swiss cheese. We used to serve them on the Outdoor Rolls at Costco (sooooo cheap!).
Potatoes are really inexpensive. We don't eat many but I know they are cheap.
Shred your own cheese instead of buying the little bags of preshredded. First, preshredded cheese is coated in something which keeps it from melting nicely, and second, it's cheaper to shred your own. The one exception I make is buying the 5lb bag of shredded mozzarella at Costco and freezing it in 1lb bags.
We eat a lot of spaghetti squash, acorn squash, etc and I save the seeds to roast (just like pumpkin seeds) then add them to my husband's trail mix for his lunches. I buy large quantities of nuts and seeds and freeze them then pull out a little of each to make a trail mix.
I recently started to make fruit topping mixins for my husband's plain Greek yogurt. We buy the big containers at Costco and he spoons in whatever topping he wants. His favorite is the cherry topping (1 cup frozen Organic tart cherries from Costco, cooked down with about 1/4 cup water and 1tbsp organic pure maple syrup then thickened with arrowroot powder). It saves money from buying the expensive Chobani or Fage cups.
I make homemade whole wheat tortillas (I've also made Paleo tortillas) which are dirt cheap to make and easy! We love to spread almond butter on them, a sprinkle of cinnamon, and diced Apple or banana before rolling them up. Yum!
I made English muffins once which were delicious but a little more time consuming...but not bad. My husband recently requested them again so I'll have to freeze some.
I freeze ice cube trays with lemon juice and lime juice for using in recipes. I put the cubes in a freezer bag. I always have "fresh" juice for my recipes which tastes so much better than the bottles! I don't know if it's cheaper, though. I also zest them before juicing them and freeze the zest to make whole wheat lemon poppyseed muffins, etc.
The biggest money saver for us is just not eating out at all. It's been 7 weeks since we've had a meal out.