Jesus, as He Himself came right out and said, came "to destroy the work of the devil", not to pay for our sins. Us not having to pay the penalty for our sin was not the specific job He came to do... it was an added beneficial result for us.
What He did was to "become sin".... thus, when He died, sin also would have to die right along with Him, no longer being able to have any power over us..... because, sin would not be resurrected when He was. (Remember how he told us that when a man died, his wife was no longer subject to him?)
So, what He meant was, "It is done... Satan has been tricked into giving all sin to me, letting me now BE all the sin of the world.... thinking that by doing this I would REALLY be crushed for all time...... But, now that I AM sin, my job is finished, all sin will die with me, whether in a few seconds, or in a few hours."