Depends on your definition of economically, we could reverse engineer a camera and build parts or the whole thing for it, but all of that takes time and skill. The scenario of sticking an object of this sort of complexity in a machine that can scan it that precisely make an exact duplicate in the same material like "that" isn't here. Combine that with the different models of cameras that would be in demand, by a small market. It would probably still be cheaper to find a machinist, job shop, good model engineer, horologist etc to make the part required.
These parts are mostly done in ABS an impact resistant plastic, it however doesn't have the wear resistance of a hardened steel gear, a 3D printed part could not stand up to the cycles or wear of an original metal part. I would also think that in most cases the resolution of the 3D print would not be fine enough for some required parts. Something like a focusing helix for example would not have the fine smoothness of fit as a 3D printed part as a solid brass machined part. While there are metal 3D printing capabilities the same resolution issues and material limitations apply.
The machinists/model engineers/horologists of today are the new 3D designers and fabricators.
You're behind on the tech. Just because you haven't been exposed to it, doesn't mean it doesn't exist.
You wouldn't want to scan and make a direct copy of a worn gear anyway. You'd want to scan and refine/remake the model in your 3D design software before printing one out.
Check out shapeways.com for examples of their material list and examples of designs.
Of course there are still many competent craftsmen around, utilising old technology (lathes, hand tools, etc) as well as new (e.g laser-cutters).
Also, er, how many focusing helices have you ever had to replace?
(Also, remember the Chinese Proverb - People who say it cannot be done should not interrupt those who are doing it).