Current SC's prices are good for renters, but not the hosts.
Simple math tells us that with a 15 TB hdd farm, I'd make 4.5 usd/month by renting all of those disks. That's based on your very own numbers.
It's not even worth the electricity.
Sia will never be a good hosting solution, it's either unprofitable for the renter or the host.
Currently the strong competition among hosts has sunk the prices of storage, right, but in the future they can easily stabilize in a fair price good for both sides. Remember: it is the host who decides his own pricing. For instance, let's consider hosts ask for $1-2/TB/month
- For renters, after 3x redundancy, that is $3-6/TB/month, still considerably lower than traditional clouds (3-7x less than Amazon S3). Good business for them
- For hosts: You can find HDDs of NAS-grade quality under $25/TB (or even 20). That means a ROI of 1-2 years. Those disks are prepared for lasting 5 years or more. Unlike mining, when you host there is not a "difficulty factor" that increases over time reducing your earnings. Are you competitive in pricing? You'll get contracts forever. And electricity costs are irrelevant. A good NAS-grade disk consumes under 4-5W, and a whole system with 4x8TB disks for instance will consume less than 50W. ROI is long compared to mining, but it is a more stable and predictable business, so it is good niche for many, specially those that have access to expensive electricity