Where I work, me and the handyman made a Japanese Water House and instead of copper guttering we made it out of wood.
We used old Ladder hooks that were in the garage (painted them black), made the 'U' Channel guttering from what ever wood that was in the workshop. Finally painted the inside with Felt roof repair paint stuff that was also in the workshop. The outside we painted a dark brown.
Looks amazing, no leaks, all recycled.
I suppose if you dont have any of that then it would be very expensive LOL