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 was going to say it's a lot less expensive if you don't need espresso. An aeropress is around $40, I bought mine nearly two decades ago, and still use it daily!
...then I realized I spent $160 on the grinder right next to it. So I'm not totally immune. :P