"In any world with magic, the rule is universal: There's a price. The way payment is taken may differ in some way." But it could also differ in lots of ways in just one world. "You are paying for changing something fundamental about reality. It's like throwing stones in a pond. It creates ripples, and no matter how big or small, the entire pond is going to shift to make room for this new change as it settles in the bottom. Might be tiny, impossible for most to perceive. But then you might have just thrown in a boulder. Big splash. Bigger ripples. And that water's got to go somewhere, now that something else is taking up the space it used to occupy."