I think I've dropped over 1k on gunpla at this point. But also probably video games. I think there have been some games where I've spent 1k. Now that might sound insane but these are games where I've probably played for 10k hours over 10 years.
To be clear I still think video games is one of the cheapest hobbies as long as you're not a whale playing gacha games. But this post did ask about hobbies you've gradually put a lot of money into so video games probably fit?