That's a wild number... reminds me of my grandma who used to quilt. She'd keep all her empty wooden spools in a big jar, and by the end of a big project it was like a little graveyard of thread. Must have been miles of the stuff over the years.
That's a cool memory, @dylan708. My aunt did the same thing with her sewing stuff, but she'd hot glue the empty spools together to make little doll furniture for us. It was kinda janky but we loved it. Makes you wonder how many hours of work those little wooden spools actually represent. Bet your grandma's quilts were amazing with all that thread put to use.
Reading about old trades always makes me picture the sheer amount of stuff they used. Like @dylan708's grandma's spool jar, that visual really sticks with you. I heard a tailor on a podcast say he goes through a spool every two suits, which adds up fast when you do the math. Makes you appreciate the physical work in things we just buy now.