Well, it seems like they were expecting the game to be a top-tier RPG franchise. It honestly seemed a bit of wishful thinking on SEGA's part, but we don't honestly know what the budget was, maybe it was really high after all.
EDIT : Granted, taking into account that AP is a multi-platform title.... I would be curious to compare these sales to other, well, let's call them 'second-tier' RPGs, like Divinity II or Drakensang.