Some of the much bigger 3D printer companies already are nearing the speed of injection molding.
The cost of a spool of filament for my printer costs about $50, granted it doesn’t run much since I only use it for a few parts at a time. I haven’t had to replace a color yet after 3 years.
Keep in mind that filament goes bad if not stored properly. Keep it in vacuum-sealed baggies until needed. Otherwise, it will absorb moisture in the air, leading to jams in the printing nozzles as the moisture heats and pops. Especially true for nylon filaments (my favorite for printing strong durable items).