Wouldn't that only be true if they replaced/upgraded everything every few months? You'd have to factor in the cost of that. And of course, it wouldn't work that way anyway because Moore's Law isn't actually continuous. It's is a line drawn through discrete points in the timeline (new product launches from chip makers).

Also, correct me if I'm wrong, but Moore's law doesn't say anything about ancillary costs like power/air conditioning. I have no idea what the trend is for those.