I don't directly but a NOVA show I saw dealt specifically with illuminated Manuscripts. The books were made of Vellum, a large one would be equivalent to a hear

I don't directly but a NOVA show I saw dealt specifically with illuminated Manuscripts. The books were made of Vellum, a large one would be equivalent to a heard of animal hides', and took years for to complete by hand. It was a rich man's luxurious novelty. My guess is that it would be equivalent to an art piece by a famous artist now. Even the cheap ones had to use parchment which is still expensive. Paper is cheap now but it was very expensive during Medieval times. It wasn't until we got wood pulp paper and automation that it got very cheap and that didn't come until the mid 1800's.