Very interesting to know, but i just looked it up and it still seems expensive in the long run. Azure's cheapest storage tier is 1 dollar per TB per month. So 5 TB of backup would cost 60 bucks a year, but a 5 TB drive costs about 120 bucks. So after 2 years of cloud backup it costs you an extra 60 bucks a year every year vs. if you just bought a hard drive.