About 48 cents in PLA at $22 a kilogram — filament, power, machine time and a 5% failure allowance included.
The 3DBenchy is the standard calibration hull, and its usefulness as a cost example is that it is small enough for the non-filament terms to be visible rather than rounded away.
The four terms on a 15 g boat
- Filament: $0.33 — 15 g, which is 5.03 m of 1.75 mm stock
- Electricity: $0.01 — 0.039 kWh at 100 W over 23 minutes
- Machine time: $0.12 — 30 cents an hour, prorated
- Failure allowance: $0.02 — at a 5% scrap rate
Total $0.48. Filament is about two thirds of it, which is unusual: on a long print, machine time overtakes plastic well before the ten-hour mark.
Print it in something other than PLA and the arithmetic moves
The mass barely changes between the common filaments, but the price per kilogram does. The same hull in PETG at $24 costs a few cents more; in PA6-CF at $60 to $120 a kilogram it costs several times as much, and it would also need a dry spool and an enclosed machine before it printed at all.
The other term that moves is failures. A Benchy exists precisely because it is a test print — if you are printing one, you are probably tuning something, and your effective failure rate during tuning is nothing like 5%.
Why it is worth costing the cheapest print you own
A Benchy is a useful sanity check on a cost model, because you already know roughly what one is worth. If a calculator tells you a Benchy costs three dollars, its assumptions are wrong somewhere and you can find out where before you trust it on a job that matters.
The usual culprit is a machine-time or labour figure applied per print rather than per hour. On a 23-minute print, a flat "setup charge" is the whole cost.
Change the material, spool price or failure rate in the print cost calculator, or check the mass against your own slicer using the length and weight converter.