score:6
My grandfather was a antiquarian book store owner in 1920s, in Kiev (Ukraine), and he bound books (I possess some books bound by him). With all ingredients ready he was able to bind 2-3 books per day, alone, with no helper. This is based on what my father told me (sometimes my father helped). But he was not binding them full time: he had to attend the store.
I suppose the process was not very different from what was done in 13th century. I do not see any substantial progress in book binding between 13th century and an early 20th century workman who worked alone and had no expensive tools. Perhaps his knife was made of better steel but this hardly changes the time required.