I disagree vastly with the majority of the answers here - there are a large number of recent NASA SBIR/other grants that show the agency firmly believes otherwise!
Currently, the 3D printer on the space station is naught but a research one and is a poor one at that. The company that made it is run by a... not so nice fellow that didn't do a good job of building it. It has served limited use due to this.
The primary cost savings could arrive through recycling of the materials onboard. This would allow for reusable utensils, reusable tools (tool broke? if you still have material, it can be reprocessed), purpose-made parts for performing experiments (recycling makes this not at all wasteful), and so on. Utensils especially are useful - if they can be recycled, they will be sanitized when the material is melted at its usual temps! Currently, astronauts must wash all of their utensils with wet wipes since running water isn't the best idea on the ISS. This generates a (hilariously silly) amount of waste in the form of nothing but wet wipes. Which also must be sent up as supplies. And the astronauts say that the utensils can get fairly gnarly after a while... so being able to print single-use recyclable utensils lowers waste generation, lowers supply requirements, and increases quality-of-life (in some small measure) for the crew. All large cost savings!
The issue isn't with the technical readiness of 3D printers for space station employment. Even the most basic of printers is capable of printing in zero-g in its stock form. The issue that requires some engineering is bed adhesion, and removal of the byproducts generated by melting ABS/PLA/Ultem-1010. These fumes can be hazardous and must be removed from the build volume with air cycling (or must be contained while the machine is running, then purged).
ERASMUS is the utensil recycling idea I mentioned - can see that it was funded here: http://www.parabolicarc.com/2016/05/06/nasa-selects-tethers-unlimited-sbir-awards/
Note that the same company/division is currently building this as well - probably not a coincidence, once you figure one of these out the rest are natural evolutions of the starter concept. Neat stuff! -