I've looked across all of the rulebooks (German version, as far as they're available), and it doesn't seem to be stated anywhere explicitly: What if I want to learn a spell from a different realm? Shouldn't this be possible at a higher cost? It isn't stated anywhere (as far as I have found) that you cannot learn spell lists from magical realms other than your own, but just giving it the same cost as a similarly restricted list from your own realm seems somehow wrong, too.
So, where are the rules for that? And what are they? Is it simply "you can only learn stuff from your own realm"?