Of course in Once Upon a Time, things don't come cheaply for something off Rumplestiltskin and he usually wants things that are precious to you or outright silly to the person, but in time is much more bigger to his own agenda's and plans.
But what did the Dark Queen Regina offer to Rumplestiltskin in return for the Dark Curse that eventually ripped everyone from the enchanted forest and most off the other magical lands.
I have watched Seasons 1, 2 & 3 and I am not sure if I am missing something but if the answer is in one of the episodes, please include in your answer.