Even so, if one develops a substantial civ level at one location, the
money that can be gathered by _one_ noble vastly outweighs what several
can gather doing common magic.
And the magicians will have to be spread out to do so... vulnerable.
I think that common magic is a good deal. But not so good a deal as to
suggest gutting it.
If Rich wishes to consider a sliding scale for the returns on common
magic, versus the civ level, I'd support that. To lessen the offence to
reality and to emphasize that it is _civilization_ that is economically
profitable.