From an economic point of view, the monastic scribal culture of (some of) the Middle Ages was autarchic. The writing culture in the modern world cannot achieve autarchy. You may write a book by hand, but you still need to purchase the paper, the pen and the refill/ink. Even if you’re a book artist, you still require paper, which you can’t make yourself.
European monastic scribal cultures were able to achieve 100% autarchy. The same monastery could, and did, make its own parchment, its own quills, its own ink. Trade wasn’t required for the basic act of writing, as all materials could be produced on site, within the walls of the abbey. Manuscripts could be 100% homemade.
Since pre-modern chirography (writing done by hand rather than by a machine) presupposed a wide knowledge of and familiarity with the technology of writing – far more than for us today –, it was an advantage for scribes to be in the centre of those productive operations, to make or supervise the making of parchment, to mix their own inks, to control the whole process of bookmaking.
The division of labour, which is the first symptom of a developing economy, didn’t elude the world of writing. If monastic autarchy was more or less the rule before 1100 AD, by 1500 AD fewer and fewer houses would make their own parchment and inks, as these were available on an increasingly competitive and therefore wider market.