When I was getting married a few years ago I started down this path as well. However I quickly realized I wouldn't be able to get the quality I wanted so I ended up finding someone who would be able to 3d print and cast my design. There are casting houses out in LA that will accept a STL file and will 3d print, cast, and finish your ring for you. The price is very reasonable, just labor and a bit of a premium on top of the spot gold price.

Using that experience I ended up starting a side business where I sell custom designed jewelry. My most popular design incorporates my customer's fingerprints. I build a pipeline that lets me go from a jpeg or other image file of the fingerprint to a fully 3d printable STL file (mostly using the blender python API). Because there are so many casting houses in LA they compete to keep the prices down. My completely custom rings that I have cast in small batches (compared to the large chains), are still very cost competitive with the competition.