Jon Snow is one of the biggest characters of the series; while Sansa is certainly important, Jon is literally one half of the “song of ice and fire.”
Although Sophie Turner understandably didn’t drop any precise figures, she did reveal in an interview with Harper’s Bazaar that Kit Harington was paid more for Game of Thrones.
According to Turner, however, it’s only fair that he took home more than she did.
Also, all those night shoots, which may have been quite unpleasant.