"3D printers are low-cost."
Since when?
Even if you can afford a printer, the conductive filaments/inks are super expensive. And, it takes hours to design and print even a single coffee mug. Advancements in technology will speed up the process and even automate the designing phase. In about 20 years, the purchasing power required to acquire the best 3D printer available in the market will be astronomical because fiat currency is probably going to suffer inflation like anything.
The smart dudes who have invested in cryptocurrency will have access to everything described in the article- good and bad. However, there are research centers that produce custom materials and the inks required to 3D DIY print.
If the government can form coalitions with these organizations, they can make use of anti counterfeiting technology to keep everything in control again- currency, commodities, products etc.