Material
(45 g + 5 g) × 5 plates × 20.00 USD/kg = 5.00
You charge everything that comes off the spool: the piece, the purge, the supports and the brim. In multicolor, the purge can weigh more than the piece.
How a 3D print price is calculated.
The same math Tobera does, one step at a time, with the example order: 50 PLA keychains sold on Etsy. Each layer of the cut is a step; tap it to jump to its math.
Electricity
150 W × 50 % × 15 h × 0.17 USD/kWh = 0.19
The power supply says 150 W, but the heated bed cycles on and off with its thermostat: on average the printer draws a fraction. That duty cycle (50 % in the example) keeps you from charging electricity twice over.
Machine wear
400.00 USD ÷ 3,000 h × 15 h = 2.00
Every printing hour uses up part of the printer: what it cost divided by the hours it will last. Hourly maintenance (nozzles, belts, the build sheet) goes on top; in the example it is zero.
Failed prints
7.19 × 8.7 % = 0.63
With 8 % of prints failing, delivering one good piece takes more than one run: the surcharge is 8 % ÷ (100 % − 8 %) = 8.7 %. It applies to what the machine uses (material, electricity, wear). Your time stays out of it: nobody sands a piece that came off the bed.
Setup
5 plates × 15 min × 25.00 USD/h = 31.25
Slicing, setting up the plate and removing the pieces. Charged per plate, in full: if the last one is half empty, setting it up costs the same.
Finishing
50 pieces × 3 min × 25.00 USD/h = 62.50
Removing supports, sanding, painting, assembling. Charged per piece, at your hourly rate.
Order cost
101.57 USD5.00 + 0.19 + 2.00 + 0.63 + 31.25 + 62.50 = 101.57
Margin
101.57 ÷ 0.60 = 169.28
To keep 40 % of the price, the cost is divided by 0.60. Adding 40 % to the cost leaves you less: margin is measured on what you charge, not on what you spend.
Platform fee
169.28 ÷ 0.90 = 188.09
The platform keeps 10 % of what you charge (18.81). For 169.28 to reach you, divide by 0.90; multiplying by the fee falls short on every sale.
What each printer hour earns
67.71 ÷ 15 h = 4.51 USD/h
Profit divided by the hours the machine spends on the order. The real margin ends up at 36.0 %, because the fee takes its share. With two jobs and one printer, take the one that earns more per hour.
The engine rounds once, at the end, and squares the breakdown to the cent with the largest-remainder method. If you redo a step with already rounded figures, it may be off by a cent.