Just putting in my thoughts on these 2 fine watches...I don't own either but do own examples from both brands, and have handled both of the watches you are considering.
I have never warmed to the MC design as I have a soft spot for the old Master Moon (it is one of the JLC's I own). But that aside my impression is that the JLC's movement is not finished to quite the same level that the GO Cal. 100 is.
I would also say that the dial on the GO is more refined, although it is a "busy" finish when compared to the JLC.
As for the costs, who knows why companies charge what they do. I think the best answer is "because they can" and it likely has little to do with production costs and volumes when compared to where they wish to position their brand in the market. I have never been to the GO factory but have been to JLC and I believe it is no secret that JLC produces more watches per year than GO does. When it comes to specific models however, it would be difficult to say that more of one are made than another unless you had access to specific numbers frome each brand.
Of the 2 options presented I would personally get the GO.
Good luck with your decision.
Cheers, Al