Re: Sounds good!
OK, we'll take those numbers. For redundancy (and a fair comparison) you need to be storing 6 copies of the data in two different locations. That puts us up to $3060 (or a 29 month ROI). Let's add some light IT maintenance to it of 1 day per year at $500 per day (because disks fail, stuff needs maintaining and monitoring). Also, I'm not sure what you're using the disk for, but everywhere I've worked doesn't like their disks to be running at 100% capacity so what does it do to the numbers if we run at 80% capacity (as it's pay per use)? All of a sudden you've got a 5 year ROI. As you said, this is before you start bringing in power, cooling, the hardware to run the disks on etc (but also before you factor in retrieval bandwidth costs for Azure too, as that will very much depend on the use case).
This ROI also isn't taking into consideration the fact that we have a $3k up front cost as opposed to a gradually increasing cost (again, pay per use) that tops out (in this example) at $100/month.
Yeah it's expensive if you're a home user wanting to keep your photos and documents safe, but for businesses where data integrity and reliability is key it's a lot closer to the cost they'd expect.