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.
I wanted, but saw that you start with a simple dobsonian, then upgrade to a newton on a equatorial mount, then a schmit-cassegrain, then a bigger mount (thousands of $), then motor drive, then goto, then 48MP CCD, then a Meade 12", then then then and you spent a fortune on it, and you can use it only on some cloudless nights :-/