[jaclaz]

Well, the actual comparison is between the cost (for ownership) of a 1 TB (refurbished) drive vs. 1 month of 1 TB of cloud storage.

The Author could have done it as the cost (for ownership) of a brand new NAS with 2x2 TB disk (which can be - just checked on tiger direct) around 350+65+65=480 US$ vs 6 months of 4 TB cloud storage 6x4x20=480, but the overall message would have been the same.

Imagine that you rent a car for 6 months and during the 6 months you pay rates equating the price of the car brand new.