Cheap to start, expensive to refill: compare a whole planned period
By Erik Nilsen · Kroni3 min read
Two products can have opposite price differences at purchase and at refill time. Your child therefore needs more than the starting price to compare them. Choose a specific period and count the refills actually included in the plan, without assuming endless use.
Put purchase and refills on one sheet
In a hypothetical example, your child considers two optional stamp sets meeting the same need. Set A costs 60 units and each refill costs 45. Set B costs 120 units and each refill costs 15. Both include the first ink supply. Your family estimates two extra refills within a concrete six-month plan. The products and arbitrary prices are invented.
With no extra refills, A costs 60 and B costs 120. With one, A costs 60 + 45 = 105, while B costs 120 + 15 = 135. With two, A costs 60 + 2 × 45 = 150, while B costs 120 + 2 × 15 = 150. With three, A costs 195 and B costs 165.
Make four rows labelled zero, one, two and three refills. B only becomes cheaper at three extra refills in this example. With the two in your plan, the costs match. A low refill price does not make B cheapest on the first day.
Separate today's budget from later costs
If your child has 100 units today, only A can be paid for now without another agreed contribution. Both costing 150 across six months does not give your child an extra 50 or 20 units on purchase day. Note when the later amounts might be needed.
A realistic snag is that the refills do not contain the same quantity or last for comparable use. Check the product information and convert the plan to equivalent use before relying on the table. Here, an identical need and two equivalent refills are assumptions, rather than claims about actual products.
If your child's interest is uncertain, keep both the zero-refill and two-refill rows. They should not promise to use more ink simply to justify an expensive start. Your family could also wait or use an existing set; that is a separate option.
Ask your family: “How many refills are actually in our plan, and can we cover both today's payment and the later amounts?”
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.
