I’ve had this conversation with other people who watch the show as well, so I think it’s interesting we’ve never discussed it before. I’ve always thought of it as, it’s not necessarily the *magic* itself that has a price. More that the motive behind the magic does. In high school I went through a “alternative religion” phase, and read books about wicca, etc. And there is something called the “rule of 3”: it essentially states that whatever magic acts you do, will come back to you threefold. See also in other beliefs: treat others as you would like to be treated, be careful what you wish for, the energy you put out into the “universe” will come back to you, etc. There are many different versions of it for any walk of life. I don’t think it’s necessarily every little piece of magic that has a price.
In regards to your question: Faeries in Once tend to do magic for *others*, not for their own means, similar to Rumple’s deals. He often reminds people that magic comes with a price, and it’s *their* price, not his for actually performing the magical act. I suppose that if they did perform magic for themselves, or for selfish reasons, that it’s very likely that they would pay a price for it.
Keeper of the Cheshire Cat’s smile, Baelfire’s sword, Snow’s backpack, Robin Hood’s bow, Ariel’s purse, Ariel’s smile, Henry’s heart, Belle’s shoe collection