This information might help you.

It was in another thread I believe, so the credit goes to them for pointing it out.

Every level of magic in a path that is not the inital cost, costs a certain number of DPoints.

8, 16, 24, 32, 40, 48, 56, 64 etc.

So the higher your initial rating of magic (Like a Titan's 3 Air, or a Moloch Fire 2, or a Cyclops with Earth 3, cost less points to get to 9 in that path by quite a bit.