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.
Warhammer 40k. I heard about the game years ago and thought it sounded pretty cool. Didn't realize that unlike D&D, it's not something generally played without minis. And it's a massive war game. So you need a lot of minis. And it's a massive war game. So you need to know how to strategize or you're gonna suck. High cost and high skill.
Wargaming is something I've always wanted to try but don't want to spend the time and money to actually try it. It's just way too high of a barrier.
There's a cool game called Moonbreakers that has great model painting tools. I hope someday Warhammer 40k gets a tabletop accurate video game with model painting and everything. I can see why they wouldn't, because it may take away from tabletop, but I'd bet it'd work the other way. It'd create a way for people to try it before committing that much to it, instead of seeing the barrier and backing out.