The part itself is trivial: a brass nozzle is a couple of dollars, a hardened steel one is a few times that, and a ruby or tungsten-carbide tip runs into tens.
The number worth carrying into a cost model is different: roughly 2 cents per printing hour, covering the nozzle and the small consumables around it. On a 10-hour print that is $0.20 of consumables against $3.00 of machine time — $6.02 all in.
Why the hourly figure varies so much
- Plain PLA, PETG and ABS through brass. Hundreds of hours before the orifice measurably widens. The hourly contribution rounds to nothing.
- Carbon-filled or glass-filled filament through brass. Chopped fibre is harder than the nozzle. Wear is visible within tens of hours, and the failure is gradual — the orifice grows, extrusion goes over-wide, and dimensions drift before anything looks broken.
- Anything abrasive through hardened steel. Back to hundreds of hours, at a higher purchase price. This is the cheap option the moment a filled filament enters the workflow.
The cost of not replacing one
A worn nozzle does not announce itself. It produces slightly over-wide extrusion, slightly fatter first layers, holes that come out undersized and parts that no longer match the calibration you did months ago.
The expensive version of that is a batch of parts that all measure wrong. Against a $2.34 to $5.82 print, a nozzle you were reluctant to change is a bad trade at almost any price.
Two costs people forget
Recalibration. A nozzle change means a new Z offset and, on many machines, a fresh bed mesh. That is hands-on time, and it is worth more than the nozzle.
The nozzle change that goes wrong. Cold-tightening cracks the heater block seal; over-tightening on a hot block strips it. Both turn a two-dollar consumable into a hotend replacement.
When to change it
By outcome, not by calendar. Print a known part, measure a known dimension, and change the nozzle when it drifts. Print an abrasive filament, and change it on a schedule instead — by the time the drift is visible, a batch has already been printed wrong.
Add your own consumables figure per print, alongside the hourly machine rate, in the print cost calculator, or compare nozzle sizes in the nozzle reference.