One other piece of information: A few years ago I quoted for gigabit broadband and phone into a large central-London-based housing sprawl (2500 flats). I could do the service for a headline £5/month/user but that required 100% takeup and given the relative lack of gigabit routers it was going to be 3gb/s total divided by 2500 users.
Granted they'd have had an excellent service, given that it would have been gigabit symmetrical at wirespeed, but their routers wouldn't have handled more than 100mbit/s via the interface and circa 50mbit/s throughput through the firewall.
Router connectivity has moved on to gigabit interfaces, but the processing power required for line-speed gigabit hasn't made it's way into the routers yet and you're lucky if you'll find something that'll process packets at over 80mbit/s in something the wife will allow in the house.