The bulk pack saves money only if its contents are used
By Erik Nilsen · Kroni3 min read
A low price per item is usually calculated using everything in the pack. If some contents become unusable before your child gets to them, the calculation changes. Also count how many items are realistically likely to be useful.
Calculate using usable items
In a hypothetical example, your child wants their own modelling material. A small pack of four portions costs 40 units. A large pack of twelve costs 84 units. The material is identical, but may dry out after opening if not used as intended. The family has checked the actual product instructions; the prices here are arbitrary teaching numbers.
The small pack costs 40 / 4 = 10 units per portion. The large pack costs 84 / 12 = 7 units per portion if all are used. If only six are used, the cost per used portion is 84 / 6 = 14 units. With eight used, it becomes 84 / 8 = 10.50 units. With nine, it is approximately 9.33 units.
The large pack therefore needs at least nine used portions to beat the small pack's cost of 10 units per portion in this example. That does not mean your child should be pressured to use nine. It is information needed before buying.
Use a concrete time horizon
Consider how many portions your child actually wants to use while the product remains usable. Start with a specific project and a cautious estimate, rather than “we will probably use it later”. If the need is four portions, the small pack meets it for 40 units and ties up 44 fewer units.
A realistic snag is your child promising lots of extra projects after seeing the bulk pack. List definite projects separately from possible ones. You can still choose the large pack, but recognise that the saving depends on the uncertain part of the plan.
Check whether unopened portions can wait until later and whether you can follow the actual instructions. Do not invent a usable storage period you have not checked. If the packaging differs substantially from this example, change your estimate.
Ask your family: “How many portions do we expect to use, and what does each cost if the rest are unused?” This is a money exercise, rather than a requirement to fill more free time with activities.
Carry the calculation into your family agreement
Kroni can keep track of your child's virtual balance. The app does not transfer money, so any actual purchase is paid for outside it. Agree on what you will record, then check the amount with your child afterwards. Do not deduct a possible cost as though the purchase had already happened. Read about allowance in Kroni.
