Just to clarify where things stand with respect to the magical creation of wealth, since this is saga-dependent. At present there is no Order-wide rule about the magical creation of wealth. A few individual tribunals have passed rules, but it hasn't risen to the point where a Grand Tribunal has addressed it.
The primary concern, as evidenced by the arguments made against the magical creation of wealth, are the attention that it draws to the Order. For example, in Stonehenge a magical-wealth rule was provoked when one covenant started to create a great deal of magical silver, which drew a lot of attention from the mundanes.
Many covenants currently use a little magic to enhance their income. But so far, few have taken it to an extreme. A magically enhanced harvest here, an augmented flock of sheep there, and no one thinks its too unusual. A common factor is that there is generally a mundane industry in existence that is enhanced by magic. Wholesale magical industry has been discouraged as being too flashy. So, casting a spell to create fish or get them to leap onto the docks is out, while using magic to assist your fishing fleet is not. Common sense has generally prevailed.
Up until now, however, equilibrium has been maintained without the need for much in the way of actual rules. The older covenants like to maintain the status quo. They use magic in subtle ways, and serve to police the younger covenants from pushing things too far. Occasionally a new covenant will come up with a magical money-making scheme that a more powerful covenant will have to quash. Always the threat of tribunal, or heaven help us, Grand Tribunal, action is used as a threat. Almost no one wants the issue settled at a tribunal, since the results will almost certainly be more restrictive than they already are. On occasion, however, quaesitors have had to get involved. And in a few instances charges have been brought for endangering the Order. So, it's not an idle threat.
As for specific rules. Stonehenge and Normandy Tribunals have imposed a limit of 2 MP per magi per year on the creation of magical wealth. Thebes has imposed a similar limit of 3 MP. Other tribunals have discussed the issue at their tribunal meetings, but have not made a ruling as of yet. These rules are generally interpreted as pertaining to the direct creation of wealth, not magical assistance in the creation of wealth. So, there's no fruit of the poisoned tree argument. If you use magic to find silver in them thar hills that you later mine, you're okay. It's if you use magic to make the silver that you're restricted.