We've seen how complicated the internals are for Canon and Nikon lenses, and now Fujifilm has released a video showing just what it takes to craft the XF series lenses for their mirrorless cameras:

Again, I personally could watch hours of this stuff, but even lenses you think are kind of cheap are not easy to make. It takes many hours and quite a few skilled workers to bring these lenses to life.

Source: Fujifilm YouTube