Additional costs — overview

A cost factor is a per-unit cost that isn’t a material: dipping labour, electricity, machine time, a cleaning cycle. You define the rate once in a shared catalogue, then attach it to a bill of materialsBill of MaterialsA bill of materials tells Assemblified how to build one unit of a finished good. When a customer orders the finished-good variant, Assemblified deducts the right component quantities from inventory automatically. Read more → or a sub-assemblySub-AssemblyA reusable assembly block that composes into bigger BOMs. Define it once, include it in any BOM. At execution time, Assemblified expands the sub-assembly into its own components recursively. Read more → with the quantity consumed per one finished unit.

line cost = quantity × rate

There is no waste multiplier — waste is a materials concept. Twenty minutes of operator time doesn’t get “wasted” the way wax does.

On this page

• Why it exists
• The two rules
• Labour vs. overhead
• Where cost factors show up

Why it exists

Before additional costs, labour lived only on a work orderWork OrderA planned production run: pick materials, build the items, do QC, and complete — all tracked together. Use work orders when you're building stock ahead of demand or running a multi-day project. Read more → and never reached the BOM’s cost. For a candle that gets dipped ten times, labour and electricity are the majority of what the candle actually costs to make. The only workaround was folding process cost into some material’s unit cost — which corrupts that material everywhere else it’s used.

The two rules

Everything else on these pages follows from two rules. They differ on purpose.

1. On a BOM or sub-assembly, cost is always live

Change a rate once, and every BOM that references it re-prices immediately. Nothing is cached, so nothing can go stale. Attaching a factor, detaching it, or editing its quantity takes effect the moment you do it.

2. On a work order, the rate is frozen — but the quantity is not

When you create a work order, each item captures the rate it saw at that moment. Editing the factor’s rate afterwards, or attaching a new factor to the BOM, will never move that work order’s costs. But changing how many units you’re building will: twenty candles cost twice the electricity of ten.

Note

That asymmetry is the whole point. A BOM answers “what does this cost to make today?” — it should follow today’s rates. A work order is a record of a job you priced at a moment in time — it should not silently re-price itself behind you.

Labour vs. overhead

Every cost factor has a Kind, and you pick it when you create the factor:

Kind	What it means	Where it lands on a work order
Labour	Human time	The work order’s Labour cost
Overhead	Everything else — power, machine time, consumable process cost	Folded into the work order’s cost totals

Never both. A Labour-kind factor is not counted a second time as overhead, which is what makes it safe to tick both checkboxes when you push a cost to Shopify.

On a BOM or sub-assembly, the distinction doesn’t change the arithmetic — both kinds roll into the same Additional costs per unit figure, because that number is the BOM’s full cost to make. Kind only decides which bucket a work order files it under.

Where cost factors show up

Settings → Additional costs Create a factor, set its rate, see what's using it.

On a BOM or sub-assembly Attach a factor with a per-unit quantity; read it back in the Costs tab.

On a work order Frozen rates, rescaling quantities, and the labour hand-over.

Pushing cost to Shopify Two opt-in checkboxes, both off by default.

Worked example

The candle-dipping sheet this feature was built from — a dip add-on applied to a plain candle:

Component	Qty per candle	Rate	Line cost
White dinner candle (raw material)	1	landed cost	—
Dip wax (virtual materialVirtual MaterialA material tracked entirely inside Assemblified — not a Shopify variant. Useful for shop-floor consumables (glue, packaging, labour units) where you need quantity tracking but don't want a Shopify product on your storefront. Read more → , g)	263.6 g	$0.0033 / g	$0.869880
Dipping labour (Labour factor, hour)	0.0166667 h	$40 / h	$0.666668
Electricity (Overhead factor, kWh)	0.1 kWh	$0.4163 / kWh	$0.041630
Dip add-on total			$1.578178

Note the labour quantity: one minute is 0.0166667 hours, not 0.0167. Quantities are fractional and kept exactly as you type them — enter the real number, not a rounded display value.

See also

• Track building cost — the older virtual work-hour pattern, and when it’s still the right tool.
• Check BOM margin and cost breakdown — reading the rolled-up cost.