Compare the cost of refilling a product versus buying new.
Refill packs strip out the container, the pump and the shelf presentation, which is often most of the price of a household product. Dividing the pack price by the number of fills it provides gives a directly comparable unit cost, and multiplying the gap by annual use gives the yearly saving. The containers avoided figure is the packaging side of the same decision.
Refill unit economics
Cost per fill = refill pack price / fills per pack; yearly saving = containers used x (product price - cost per fill)
Usually per unit of product, but not always — check the volume. Some refill pouches hold less than the bottle they replace, which erases the discount.
Concentrates are meant to be diluted to the stated ratio. Comparing prices only works when both are measured at working strength.
Fewer containers means less packaging and lighter shipping, which is the reason many people refill even when the saving is small.