I guess its because when the figures are really high, most people run around switching everything off, resulting in minimal costs anyway. (Just loads of stress)
The problem for me was that I could not do this. At my worst (mid July) I had 2 days of $40 each in a row, but I was at work.
Ouch. Didnt make sense when some here said the spike period of many days cost me $30 lol