Ezzelino, as I noted before (see Card & Board Games ARCHIVE & LINKS), this article from 2003 does not help a lot to determine the amount of silver needed to cause a significant change of its value in the England of the end of the 12th century:
What is very hard to assess about medieval money is, how quickly it could leave an area where it was abundant. Here face value worked to keep local coins in the domain of their minters' authority, while metal value allowed it to spread - theoretically all over Europe and into the East. That makes any quantitative theories about actual effects of medieval inflation a touchy topic.
I also already gave a quote of a more recent book containing similar data to Claughton's article before (see https://forum.atlas-games.com/t/the-break-room/102/1 ).

It's interesting to note that enforcing £2/magus/year, in a Tribunal with a population of the order of 100 magi, means an increase of the circulating silver over 50 years of only £10,000, which would have been pretty safe. At the same time, a limit like £20/magus/year (a Typical source of Income for a Covenant of 5 magi) would have yielded £100,000 over 50 years for the Tribunal, thus being beyond the safety margin. Some Stonehenge Quaesitor had a pretty good score in Artes Liberales!
Now, once we know that we are handling lower limits here, that's a reasonable use of the article of Claughton.
Cheers