When Alpha came out, Orcs must've thought they were kings of the world. All their spells cost ! Now, obviously Ironclaw Orcs is supposed to cost two mana, but what about Orcish Artillery and Orcish Oriflamme?
Those two cards inadvertently received casting costs of , later changed to and respectively in Beta. The switch is not to be seen as a "changing" of their costs – they were never intended to cost two. It was simply a pair of misprints.