> the monochrome version is typically 20% - 30% more expensive than the color version, which is counterintuitive...

The market for monochrome sensors is very tiny compared to the rest of the commercial products. Every phone now has 2 or more cameras on it, and there are billions of those.

Any changes to the manufacturing steps means more setup and effort. Different test procedures, quality control, documentation, etc.. That is all overhead, to be absorbed by a relatively small production volume.

I'm surprised it is only a 30% premium, I'd have expected higher actually.