> not to mention actually _downloading_ of the data from the Sia network will take that $1.50/TB/mth to $70/TB/mth
You really need to back that math up.
Here's my math: 10mbps is over 3TB per month at max utilization, so let's say it's good enough for either 2TB throughput with semi-even use, or 1TB throughput if the use is really focused on part of the day.
When buying transit in bulk in the US, Google tells me that 10mbps was very roughly $8.50 a month in 2017, $4.50 a month in 2018, and $2.50 a month in 2019.
Are you expecting the data to be rebuilt every single day or something?