||the question is the bore geometry and, as mentioned, the nubs for the encoder.
Anyone with access to a lathe and bridgeport could easily modify off-the-shelf gears to make an aluminum set. If done in reasonable volumes, the cost difference should be reasonable compared to paying a commercial additive manufacturing company to make them.
That being said, the original plastic gears lasted pretty damn long. A 3D print with a well selected material could be adequately durable.