Whats a hobby/craft that you wouldn't expect that has an incredibly high ceiling either monetarily or in sheer skill?
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.
long-distance unsupported endurance cycling. This style of riding is non-competitive in nature, and self-sufficiency is paramount. When riders participate in randonneuring events, they are part of a long tradition that goes back to the beginning of the sport of cycling in France and Italy.