$120/year for 1 TB is more than 9 times what I'd pay for 5 years of a 1 TB internal SATA
please indulge me. you said you could run the same setup for 9x less than $120, over 5 years, right? so $120 / 9 = $13, over 5 years is $13 / 5 = $3 per year, right?
i'm no mathologist, but i'm pretty sure the $47 / year in power is already a lot greater than the $3 / year you quoted, right?
you all you did was factor in the cost of the drive itself, that's $50 for a 1TB drive