Does a 0.6 mm nozzle cost less to print with than a 0.4 mm?

Cheaper overall, but the two cost terms move in opposite directions.

The same 60 mm cube at 20% infill, printed at 60 mm/s:

Why the big nozzle uses more plastic

Extrusion width follows nozzle diameter: 0.45 mm lines against 0.68 mm. Every perimeter, every solid skin and every infill line is thicker, so a fixed geometry contains more material — 63,409 mm³ against 57,824 mm³ here, about a tenth more.

That extra plastic is not waste. It is thicker walls, and on a functional part it is usually a strength gain you would otherwise have paid for by raising the wall count.

The two terms therefore pull against each other, and the machine-time saving wins comfortably. It would take filament at well over triple its normal price before the larger nozzle stopped being the cheaper way to make this cube.

Why the time falls so hard

Three terms improve at once, which is what makes nozzle size the most effective single change in a slicer profile:

• Line width goes from 0.45 to 0.68 mm
• Usable layer height goes from 0.3 to 0.45 mm, so 200 layers instead of 300
• The flow ceiling widens from a published 8–25 mm³/s band to 15–40 mm³/s

Speed alone gives you one of those. This gives you all three, which is why doubling the commanded speed on a 0.4 mm nozzle usually hits the flow ceiling and does nothing.

What it costs you

Detail, and only detail. Fine text, thin walls under 0.6 mm, small holes and crisp small features all suffer. Layer lines at 0.3 mm are plainly visible.

For functional parts, jigs, brackets and anything large, that is not a cost at all. For miniatures it is disqualifying. Keep both nozzles and swap; the nozzle itself is the cheapest part of the decision.

Time each profile in the print time estimator, then hand the hours and grams to the print cost calculator to see which is cheaper for your spool price and hourly rate.