Akroma's Memorial (M13 10.66)
Baneslayer Angel (M10 13.50, M11 13.22)
Leyline of Sanctity (M11 18.61)
Liliana Vess (M10 10.47, M11 10.38)
Master of the Wild Hunt (M10 16.15)
Primeval Titan (M11 17.03, M12 16.97)
Serra Ascendant (M11 11.88)
Sorin Markov (M12 14.62)
Steel Overseer (M11 11.31)
Time Warp (M10 12.25)
Thundermaw Hellkite (M13 12.97)
I am excluding M14 from this listing of most expensive cards because it has yet to rotate, but Mutavault and Scavenging Ooze will most definitely join this list.