One additional new bit of info on this: the time to print something can be large. I saw a lovely 3D-printed model of a cut-away jet engine online, with a mention in passing that it took 100 hours in the printer! So before we get large quantities of these available, that may be something that needs to be improved.
By way of comparison, let's assume that making the "master" (whether a styrene mold, silicone mold for resin, or computer file for 3D printing) takes some significant amount of time, then the time to crank out a kit ranges from a few seconds or minutes (injection molded styrene) to a few hours (resin) to a few days (3D printing). Just another point of comparison.