Cheapest food this side of the dumpster: Salvage grocery stores
What happens to that bag of cookies on the grocery shelf once it has passed the "best if eaten by date"? The cans of green beans that are dented in shipping? The cans of something from which the label has been torn? They may well end up in that little-known outlet, the salvage grocery store.
These stores buy up the groceries that the full-price retail chains would be too embarrassed to have on their shelves. The products are still edible (albeit perhaps stale), and sold at a steep discount. As you might expect, though, the selection can vary greatly. After all, who can predict just when the clod on the forklift in the grocery warehouse is going to drop a skid of pineapple juice off the dock?
