Edit: so it turns out that every hobby can be expensive if you do it long enough.
Also I love how you talk about your hobby as some addicts.
Probably gardening.
A few seed packets and some dirt turns into building nice cedar raised gardens, filling them all with great quality soil, expensive liquid fertilizers, various irrigation systems, and so on. And I can’t just haul all that dirt in my sedan… But hey, I have 20+ tomato plants, and about as many different pepper plants every year.
It’s honestly nowheer near as expensive as some of my other hobbies, but on the “a lot more money than I expected” scale it’s up there.