‘This one’s on me.’ He doesn’t say ‘no cost this time’ because it’s magic. There’s never no cost. He says ‘this one’s on me.’ As in whatever price there is to pay, he’ll be the one paying it.

Worried Cora may be close to locating the portal into Storybrooke, Regina and Rumplestiltskin/Mr. oro devise a plan that would kill anyone entering it; which would also put Snow White/Mary Margaret and Emma's lives in peril