[HALtheWise]

One key factor you didn't include in this calculation is "overprovisioning", the industry term for the fact that you only need to spec your total network capacity based on peak load times, and at peak times it's not actually going to be the case that every customer is using their maximum contractually available bandwidth. The typical industry assumption is that this is something like a 10x factor, although as network connections get faster, this becomes more pronounced.