Cost calculator
The calculator reads the same catalog as checkout: price, pricing unit, minimum, maximum and step come from the live offer, and the total uses one formula on the client and on the server.
How the total is calculated
Formula: total = quantity × price ÷ pricing unit. An offer's pricing unit is 1 or 1,000. The total is rounded to the smallest currency unit using round-half-up. Before payment the server recalculates the total; if the offer changed, you see the new amount and confirm it separately.