There are fabrication methods that are better suited for certain tasks. When I embarked on this project, I wanted to choose objects that fascinated me by their interlocking movement. At first, I printed two objects, the bound nut in the screw, and the print-in-place bearing.
These two worked fantastically but were slightly too large to fit in the gumball capsule. Though they both moved straight from the printer! Commonly referred to as print-in-place prints, these types of 3d prints use special internal geometry to avoid being fused together while still having tight tolerances so that they don’t wiggle out of position. I have used a print-in-place hinge for my laptop stand for about a year now and it has held up wonderfully, the only issue with these types of prints is that they can move laterally from their intended use. For example, the screw that moves as the nut’s threads interact with the threads of the screws doesn’t just rotate, but it also gets “stuck” on the ridges of the nut. additionally, since these prints cannot be printed with conventional supports, they cannot have any geometries that prevent the moving part to be printed without support.
Knowing that my prints worked, I started to scale them down. I printed 6 micro screws with the FDM Prusa printers. They also worked (albeit not as preceise as the larger screw)! 
Now was the hard part. The SLA prints. I have never used SLA to print anything before this and so I was not expecting the difficulties I faced. I had a notion that the SLA printers were more precise than FDM, but I was not expecting fusing to be an issue. I had originally printed the micro screws in SLA, but they fused together and were just an outline of what it was supposed to be. Later, I printed a version of the gear bearing I initially printed with the FDM printers.
After removing the supports and giving it the isopropyl alcohol bath, I realized that the gears of the bearing fused together, just like the micro screws. But at least it still came out in one piece and fits in the gumball!
How much did your impossible object cost? Clearly document your calculations, including raw materials, labor, and machine time.
According to 3DPrinterOs, the FDM prints would have cost, $0.09, $0.36, $0.41, and $0.46. All of which means it was a total of $1.32 for all the FDM prints including the failed 3d prints. Since the resin printers were also small, it can be estimated that they cost at most $1 for the prints including failed prints.
I did ask for help from the lab assistants for about 30 min, which is paid at $10/hr.
The Machines were running for a total of about 9 hours for the FDM printers and 4 hours for the resin printers.
All of this brings the estimated cost to around $10 for most notably, the time of the lab assistants and materials. There is an inherent opportunity cost associated with taking up a printer for 9 hours as well as normal wear and tear of the printers, but it is marginal or too difficult to accurately calculate.
The STL files for the Screw with the integrated nut is here while the STL for the bearing is here.
Happy printing!
