Steam offers downloads of Barrier X for Windows for free. (iTunes offers it for the same price for iOS, and Amazon and Google Play offer it for the same price for Android.) That's $3 off list and the lowest price we could find.
Also available is the Guild Wars 2: Heart of Thorns Deluxe Edition for Windows for $36.99. That's $38 off and the lowest price we could find. This edition includes an additional character slot, miniature revenant Rytlock, revenant finisher, Mordremoth's Bane guild hall decoration, and Heart of Thorns glider skin.