I've been trying to make sense of how the ArM economy for magic books works in the setting, and something isn't adding up for me. As I understand it, books on magic are supposed to be rare, with magi paying vis for new tractati and perhaps only Durenmar having anything close to the complete collection of books written on magic. But what causes this rarity?
A non-gifted scribe, paid in silver, can copy a tractatus on hermetic magic twice per year, provided they've been given some basic training in magic theory. So why don't covenants hire a bunch of scribes to lots of make copies of their books, then trade them to other covenants for great profit?
I've seen some plausible seeming explanations, but they don't seem to work:
Explanation 1: Scribes have to know magic theory or the text is corrupted. But it's easy to give a scribe a point in magic theory; any magus worth his salt can Train it in a single season if they extend their parma to cover the scribe. Alternatively, if larger numbers of scribes are needed a mundane person with a few points in Teaching can be hired, Trained in magic theory once, and can then Teach it to all the scribes at once. At most, once in a generation a magus has to give up a couple of seasons and the scribes don't make anything for a year.
Explanation 2: It's impossible to hire that many scribes per covenant - there aren't too many around, and those who do exist mostly don't want to work for a bunch of creepy mages. But even if you can't find any qualified scribes, there are bound to be people who are reasonably intelligent, don't quite fit in with normal society anyway, and would be happy to work in the covenant if it meant free scribal training and a job for life. Just go through the local villages finding people like that, and hire someone to teach them the required Latin 3 and Artes Liberales 1 once they get to the covenant. It costs a little more silver up front, but nothing a reasonably prosperous covenant couldn't handle.
Explanation 3: The cow and calf rule prohibits you from copying books. But there's no reason you can't make copies of books written by a magus at your own covenant. If a covenant has a magus capable of writing a high quality tractatus, then she can write many more high quality tractati - so it would be very profitable for the covenant (or the magus) to recruit a bunch of scribes as described above and sell her books to everyone for hundreds of vis in profit.
But it's obvious that this hasn't been happening, as books are very rare, including high quality books. Why not?
This is a question about the setting, not a complaint about the option being imbalanced in terms of game mechanics. Even if the Storyguide decides they're ok with the players trying this, there have still canonically been hundreds of years during which the Order of Hermes has not exploited this technique. So...is there an in-story reason why it hasn't happened?