Make in batches, and know what each unit really cost

Write the recipe once: materials, packaging, the steps and the time each one takes. A production order takes the materials off stock, adds the hours worked and puts the finished goods on the shelf under their batch number.

The cost of a unit comes from what you actually paid for each material, the hours actually logged and your share of overheads. When a supplier raises a price, you see which products it touches and what their margin is now.