I can think of a couple people I know who work in high-end manual work but they both work effectively alone. One does old-school illumination and another makes

I can think of a couple people I know who work in high-end manual work but they both work effectively alone. One does old-school illumination and another makes expensive handmade watches. Both are what would probably qualify as "master craftsmen" both in the sense that they're at the top of their game in their field and that even if they don't necessarily have people working under them (one does, the other doesn't) they at least are both passing on their knowledge (the one who doesn't have employees still teaches a class for others to learn illumination). I'm not sure this is the sort of thing that lends itself well to vertical integration due to the radically different set of skills required and maybe most critically, low volume of the final product. For example, making high-end ink has entirely different skill and material requirements from making high-end illuminated pages. But someone who makes high-end ink can produce in much higher volume than a single illuminator requires (not to mention it takes more than just ink). Likewise for watchmaking, the manufacturing of most of the parts can be generalized and scaled up while any individual watchmaker only needs so many gears and springs and such.