Wait a minute: How much money can 3D printing ACTUALLY save you in a year?

A 3D printer produces and XBOX Prototype controller in the Model Shop, on Tuesday, May 14, 2013 in Redmond, Wash. (Photo by STEPHEN BRASHEAR/Invision for Microsoft/AP Images)

A wave of giddy headlines has announced that a new academic study proves that buying a 3D printer is not only affordable — but a money-saver. In fact, the research is said to show that the gizmos save users so much money (by allowing them to print stuff they’d otherwise have to buy), they essentially pay for themselves in a year (Case in point: "Household 3D Printers Can Pay For Themselves In A Year," raves Gizmodo.)

Not so fast. The actual study – as opposed to the abstract or university summations of it — is pretty interesting, but it also raises a few questions. I got curious precisely because I love the idea of 3D printers, can think of lots of fun things to do with one, and would love to inform my wife that the data is in, and we have to spend $1,500 to $2,000 on one of these things, pronto. It’s the financially responsible thing to do! Think of all the money we'll save!

Reading the study, however, I realized that this conversation would have to wait. Instead I needed to get one of the researchers involved, Joshua Pearce of Michigan Technological University, to clarify a few things for me.

First, some basics. To investigate the economics of consumer-level 3D printing today, Pearce and his colleagues came up with a list of 20 objects for which 3D designs are readily downloadable from the open-source Thingiverse site. They concluded the cost of buying these goods on the open market would cost somewhere between $312 and $1,944. The cost of printing all 20? A mere $18.

The researchers neatly addressed some obvious potential objections. They were pretty conservative in their marketplace cost estimates (often ignoring potential shipping charges, for instance) and stuck to realistically fast and easy printing jobs. Finally: Many of the printable wonders found in the Thingiverse fall in the realm of toys, art projects, and weird fun; nothing wrong with that, but the researchers rightly picked stuff that was more practical, in order to make a replacement-cost argument.

Still, the coverage I saw was vague or selective about that 20-item list. 3D printers work by building solid objects out of a melted filament, and I was having trouble imagining what 20 plastic little doodads I might need to buy in a given year. It seems to me that to make a case about how much money a 3D printer might save, you have to start by establishing a baseline about likely spending.

First, on the low end, buying these twenty items could cost as little as $312, per the study, and not $1,944. Second, looking at the full list in a table at the end of the paper (below), every individual item on the list seemed reasonable. But as a group they struck me as odd. What’s are the chances of someone needing an iPhone 5 dock and an iPhone 4 dock? A set of shower curtain rings seemed like the sort of thing one might have to replace at some point, and I suppose it’s possible that I’ll covet a “pierogi mold” some day. But how many people are printing garlic presses each year?

So, really, where did this list come from? Is it based on, or does it correlate with, some sort of real-world data set about things an average consumer buys in a given year?

“It was pseudo-random,” Pearce cheerfully concedes. As the researchers combed through the Thingiverse, they looked for stuff a typical American might buy, “in our opinion,” to settle on “a representative group of things.” And they pretty much made stuff they actually needed. (This explains the two iPhone docks: two researchers, two docks.) That’s admirable, of course, but it’s not terribly persuasive as proof that you would actually have cause to buy $2,000 worth of stuff you could have printed in the year ahead.

Still, when I suggested to Pearce that I’d be much more convinced by actual case studies that correlated to genuine consumer purchasing-vs.-making patterns, he stuck to the core contention that 3D printers really are potential money savers. Certainly it’s fascinating to learn that even a home-printed shower-curtain ring beats a mass-manufactured rival on price, and it’s possible (as Pearce argued to me) that once you have one you think of more useful things to do with it.

Also, pointing out to houseguests that your shower rings are 3D-printed is a far better conversation starter than explaining that you bought them at the local Target.

I will concede that it’s plausible that as these printers improve and the costs come down, it may be possible to demonstrate that they pay for themselves. But all those headlines saying this already happened, and it’s been proven? Purely manufactured.