Sf has a population of over 6 and a half million and covers 600 square Km. I woudl love to see your estimate for how much that woudl cost to build and maintain.
Less than 100M to implement and under 10M to maintain per year.
I definitely don't think it's expensive compared to the benefits. Personally, if I'm pipe dreaming, I'd rather have ubiquitous 1gigabit fiber, which google pegged at 11Billion for almost all of the US to be covered.
