The same extra cost in both offers: useful for ranking, essential for budgeting
By Erik Nilsen · Kroni2 min read
When two offers have exactly the same required extra cost, that cost does not change which offer is cheaper. You must still include it when checking affordability. Ranking and budgeting answer different questions.
Calculate the difference and the totals
In a hypothetical example, your child wants an optional pen requiring a particular holder. Pen A costs 27 units, pen B costs 34, and a suitable holder costs 18 for either. The arbitrary figures are invented. Both pens meet your child's needs, and they do not already own the holder.
Without the holder, the difference is 34 − 27 = 7 units. Including it, A costs 27 + 18 = 45 and B costs 34 + 18 = 52. The difference remains 52 − 45 = 7. Adding the same amount to both does not make B cheaper.
However, neither purchase fits a budget of 40. Pen A alone at 27 fits, but the complete solution at 45 exceeds the budget by 5. The shared cost cannot disappear from payment merely because you omitted it from the comparison.
Check that the extra really is identical
A practical snag is saying “the holder makes no difference” and interpreting that as free. Write “same cost for both” beside the difference and retain the holder in both totals.
If A actually needs a holder costing 26 while B needs one costing 18, the cost is no longer shared. A then totals 53 and B totals 52, reversing the ranking. You can simplify the comparison only when the extra truly is equal and equally necessary.
Ask your child which option is cheaper and whether it can be paid for now. A correct answer to the first question does not guarantee a yes to the second.
Ask your family: “Which cost is equal in both offers, and have we still included it in the payment?”
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.
