I have found (in my organic store) that prepared canned beans are cheaper per pound than dry beans (even in bulk)--this defies all logic, I know, but it's true. My husband also requires a low-sodium diet, so I make concessions for him with regard to salsas, pasta sauce, the canned beans, and black olives. Mayonnaise is another hard-to-replicate-without-tons-of-sodium food, so I buy eggless mayo that's low sodium.
I have big, nasty food allergies (wheat, gluten, dairy), so I buy canned coconut milk, pre-bagged rice flour (if I could find it in bulk, I'd buy it), and substitute calcium carbonate powder for baking soda (low sodium) when I bake.
Food allergies and ongoing health concerns sometimes make convenience foods a necessity because they cannot be replicated from scratch. For this reason, I keep the shopping list short and stock up during sales.