Ask a print farm what a part costs and you will usually get grams times price per kilo. For a 182 gram desk organiser in €25/kg PLA, that is €4.56. It is a real number, it is easy to calculate, and it is not the cost.
Here is the same part with everything counted, taken from a farm running eight Bambu printers and selling on three channels.
| Line | Amount | Where it comes from |
|---|---|---|
| Filament, 182.4 g | €4.56 | Grams reported by the printer, FIFO against spools bought |
| Purge and support, 14 g | €0.35 | Reported per AMS slot |
| Machine time, 4h 12m | €2.94 | Depreciation + maintenance + overhead per hour |
| Energy, 0.58 kWh | €0.20 | Model power profile at own kWh rate |
| Labour, 9 min | €3.75 | Minutes per handling step, set per product |
| Packaging | €0.61 | Per-shipment consumables |
| Failure allowance, 18% | €2.21 | This part's measured failure rate |
| Channel commission | €3.03 | bol.com, per category |
| Payment fee | €0.45 | Per transaction |
| Shipping, net | €2.25 | Paid minus charged |
Total: €20.35. It sells for €18.95. Every one of those sold loses €1.40, and it sells 23 a month, so that single listing quietly costs €32 a month.
The two lines that do the damage
Labour is €3.75 — almost as much as the filament. Nine minutes of someone removing supports and packing is not free, and it is the line every spreadsheet omits because nobody is holding a stopwatch.
The failure allowance is €2.21. That is not a safety margin somebody picked; it is this part's measured 18% failure rate across the fleet. A print that dies at 68% burned filament, hours and energy, and someone cleared the plate.
Why measuring it changes the decision
The obvious response to a product losing €1.40 is to raise the price by €2. But when you break the failure rate down per printer, almost all of it comes from one machine. Route this part away from that printer and the same product at the same price turns €0.81 positive.
You cannot find that with an average. You find it by charging each failure to the machine and the order that caused it, which means the data has to come from the printers rather than from a form somebody fills in.
Note. Every figure above is marked in the app as measured or estimated. A cost model that will not tell you which parts it guessed is not a cost model.
