What is cumulative cost?

Cumulative cost is the sum of every cost paid since a chosen start, whether that start is a project launch, a purchase date or the first day of a plan. It differs from the cost per period because it keeps growing even when each individual payment is small. It matters because decisions based only on this month's bill can hide a total that is much larger than expected.

How it works

Each period adds its cost to the running total, so the cumulative figure never falls unless money is refunded. If costs are constant, the total rises along a straight line. If costs rise with scale or time, it curves upward, and if early costs are heavy and later ones light, it flattens.

Comparing cumulative cost against cumulative revenue shows when an activity breaks even. Comparing the cumulative costs of two options shows which one is cheaper over a chosen horizon, which can differ from which one is cheaper in the first month.

Example

Say a company can buy a machine for 10,000 with 500 a month in upkeep, or lease one for 800 a month. After 12 months, buying has cost 10,000 + 12 x 500 = 16,000 and leasing 12 x 800 = 9,600. After 36 months, buying has cost 28,000 and leasing 28,800. Leasing is cheaper early and buying is cheaper later; the lines cross near month 33. Illustrative numbers only.

In a game economy, cumulative cost shows how much currency a player must spend in total to reach a late upgrade tier, which tells designers whether the full path is within reach of free players.

How to model it in Machinations

Use a Drain or connection for each period's cost and a Pool that collects what the Drain removes, so the Pool holds the running total. Chart that Pool over time. Play with different cost rates as Levers and add a Register that subtracts cumulative revenue to mark the break-even step.