Don't you think the popularity of the gold iphone has more to do with having an easily recognizable latest and greatest iphone? The new one is the only gold one, so people can see your status symbol from across the room. Couple that with it being the ONLY outward change for the new model, and i think you've got your reasons. Honestly, if apple had released the 5s in almost ANY new, neutral color, it would have sold more than the black and whites too (and probably even the gold one since it's ghetto fabulous).
Also, I agree that the gold s4 is a troll by samsung- those promos are 2nd year GD student tacky.