The 9x figure was a rudimentary calculation that didn't factor in all costs, just estimated a $65 1TB drive with a 5 year lifetime. $120*5 years = $600 / $65 = 9.23. Factoring the electricity costs (which I over estimated for my region - actual cost is 7c/h for most of the day, 12.8 during peak times and 10ish during mid-peak hours. Also the cost of the drive was over-estimated, actual drive on newegg.ca was $60 for a toshiba 1TB drive)
$47.45*5 + $60 = $297 - so it's twice as much. 1.68 times if you factor a 2nd backup drive.