Because scarabs are special (e.g., more of them means they all get more hp, and can devour bigger targets, and they're airborne to boot), I figured a cost to evolve was a good move. The comparable cards, graboid-shrieker, just turns into something with a high attack and no special abilities. And it costs you an alternate element quanta to evolve.
But I submit that more ways to get your scarabs going is a great thing. Pharoah/scarab decks are slow and ugly. It's the element of time, and it loses out to "real" rushes from other elements. Unless you get lucky and manage to stall your opponent with reverses/eternity while powering through with an hourglass.