For example, I’m sure the average joe doesn’t know just how expensive calligraphy pens can be, or how deep the rabbit hole goes on video game speedruns.
Mechanical watches. I guess I grew up with quartz watches and only learned about the existence of automatic watches a few years ago. Marvelous things they are, and of course, high watch brands like Rolex, etc, are tens of thousands of dollars, with certain pieces going for millions. Insane.