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.
The thing is, it's a skill that pays for itself if you have enough projects in mind. I've paid for my equipment a hundred times over by building things that would have cost a hell of a lot of money to have done.
For my jeeps: cargo rack, front and back bumpers, pull out drawers, rock rails, body work, frame repair. Built a boat trailer, fix broken equipment, I've lost count of the things, frankly.
I think welding is a life skill like woodworking/carpentry/plumbing/electrical, they all pay for themselves as hobbies if you decide you aren't spending your life in front of a TV.