He's probably just saying that even with an initial (some kind of) magic school, spells are cheaper, and it's still easier to learn magic than to wait for something to happen and when it will happen, but the argument is really not very strong.

I highly doubt that's what he meant – that spells become cheaper, although now he could write that... he was writing specifically about the magic school. But the Castle is remarkable because it has the opportunity to learn all of this, unlike, say, the Rampart or the Necropolis. This is not enough to say that the Conflux is stronger than the Castle. Although, if an Armageddon really appears in the Conflux, it will be difficult for the Castle to argue with such a situation... :)