SR4A, p. 194, says magicians "generally [charge] around 100 [nuyen] an hour (per magician)" to create wards. That not only seems low to me (hell, high-end lawyers bill several hundred dollars per hour), it also doesn't account for differences in the mage's ability.

Does 100 times the sum of the magician's Magic attribute and initiate grade sound fair? I.e., a mage with Magic 5 and two initiations under his belt would charge 700 nuyen per hour for his services.

That's pretty much how I did it. Except that I only count initiations when metamagical techniques are learned that are further used to create a special ward. Like charged wards and reflection (?).

Same goes for healing spells and the like.

What's the value of a point of karma? A ward can be made permanent by paying karma equal to the ward's Force; how much of a surcharge gets added to your bill if you want that service?

The general consensus seems to be 2500¥ per point of Karma, just like in the character creation system. But I also modify this for more experienced (and thus: qualified) mages, by about the same 100¥ per point of Magic, and the practitioner's general attitude (as well as the customer's attitude )