Ok. This is a question that many people probably haven’t tried (because no access to a 3D printer) but has anyone tried 3D printing a cube? And if so was the performance good?
Actually, I have quite a lot of experience with prototyping speedcubes using 3D printers.
As of now, the technology isn't good enough to make something on par with something injection molded, but if you have designing experience, you might be able to design your own cube with decent performance and 3d print that.
That said, the cheapest option (FDM/Fused deposition modeling using PLA filament) usually results in much more brittle puzzles that really don't respond well to lube (You will likely experience a couple breakages on cubes printed using FDM), so I'd only recommend that for novelty purposes or very early-stage prototyping. Not just that, they will be very loud and scratchy, and you will need to sand them down to mitigate this; excessive sanding might hurt the performance, so be mindful of that.
If you order SLS parts off of Shapeways, you will be able to make something that is more realistic and competitive with injection molded cubes. That said, it's exceptionally expensive (~$300 USD per cube). So I'd recommend that if you are prototyping a cube near the middle-end of development. If you were looking for something to use in a competition, this might be the better bet, but it is an admittedly massive investment. Not to mention, they do like to collect heavy amounts of dust and residue, so they aren't exactly pretty after a long while of using.
In both instances, both will have some added performance issues, such as extra catching due to rougher textures and a much sandier feel, though with neater turning, it shouldn't be a significant issue.
Tl;Dr: It is possible to 3D print a speedcube, though if you want something viable, you will need to fork out a pretty penny.
Edit: I highly recommend you put three drops of any silicone lubricant once assembled; these cubes are bone dry once assembled, and will preform poorly.. they will get significantly better once a small amount of lube is added.
