As shown below, this part (including auto-generated scaffolding) was approximately 100 grams. The print time was approximately 4.5 hours (plus time to set-up the printer, run the slicer software, and clean up afterwards). Using these numbers, I can estimate some costs associated with 3D printing:
- Material costs = $30 – 40/kg for a spool of PLA; this bookend used about $3.50 worth of material.
- Electricity usage = the Robo3D printer has a power requirement of 360 W (12 V at 30 A); assuming it was running at full load for the entire time, it would have used $0.16 of electricity (0.36 kW × 4.5 h × $0.10/kWh).
- Capital replacement and maintenance allowance = assuming straight-line depreciation over a completely arbitrary period of 450 hours (i.e. I'm guessing I could print 100 of these before overhauling or replacing my printer—hopefully it lasts longer than that, but maybe I'll want to upgrade to a newer model by then anyway) and a printer cost of $600, I'll allow $6.00 for this category.
- Labour = Doing this at home as a hobby, I'm obviously not paying myself, and defining the amount of labour time required is actually rather difficult—someone should be nearby while the printer is running to shut it down in case things start to go wrong (e.g. the print comes loose from the print-bed so that new layers aren't aligned with lower layers), but intervention in normally only required to set-up before a print job and clean-up afterwards. A feasible commercial arrangement could have one person (say, making $20/hour) monitoring around four 3D printers. Adding 30 minutes for set-up and clean-up to this job yields a labour cost of $25 (since 4 can be printed concurrently with 5 hours of labour in this assumed arrangement).
- Total = $34.66.
Using assumptions that I feel are reasonably realistic, I came up with a cost of a bit less than $35 for a 100 g 3D-printed bookend. By far the biggest cost factor is labour, so doing 3D printing as a hobby is easier than trying to make a business of it. Still, the cost isn't too bad for things where people would be willing to pay a premium, such as customized items.
As I downloaded the design for this bookend from Thingiverse, I didn't consider any costs (e.g. labour, cost of design software) associated with making a digital 3D design.
Of course, to really start a 3D printing business, you'd also need to consider other overhead, not just the printers themselves, and a further margin for profit/ROI.