They have Diablo III AND a pre-order for the upcoming Reaper of Souls add-on for $60
The Diablo III PC digital version, normally $39.99 is now only $19.99 in anticipation the end of the auction house on March 18, and the new add-on release on march 25.
If you didn't dive in, the new enhanced loot system, the end of the auction houses, the upcoming add-on, and the new low 50% off price might make you change your mind.
Now you don't have to wait for an Xbox One or PS4 version that comes with the add-on included for $60. You can get the same deal on the PC. Or just get an improved version of Diablo III for 1/4 that.
And if you like Diablo III then also consider trying similar ARG dungeon crawlers like: Grim Dawn(still in alpha on early-access), Torchlight 2(art looks like WoW sort of), and Path of Exile(free to play) on steam.