Consider that PS4 will be sold for a couple years with identical specifications. Manufacturing cost will drop while yield increases, memory gets cheaper and so

Consider that PS4 will be sold for a couple years with identical specifications. Manufacturing cost will drop while yield increases, memory gets cheaper and so on. Eventually they will move to a smaller case, further integrate chips shortening the BOM, reduce power supply demands and so on. Look at the different PS1, PS2 and PS3 revisions on Wikipedia, it's quite the lesson.