If you have an air fryer, tofu slabs!

Slice a block of tofu short-ways into six to eight slices. Season on each side with oil and choice of seasoning. I use adoboe seasoning, garlic salt, paprika, and other savory flavors. Lay in a single layer in the air fryer and fry for 15 mins at 400 F, flipping with tongs halfway through. Put on bread, add condiments if you want, and eat. Leftover slices can be put into the fridge and either reheated or eaten as cold cuts.

Where I am, this works out to less than a dollar per sandwich, and makes a complete protein. Add some lettuce and tomato or other veg for more flavor, fiber, and vitamins if you can swing it.