It's funny that I have symetical LAN Gb all over my house and beyond the initial cost it costs pretty well $0 per month to operate and maintain. My ISP gives me a limited use Gb line outside the house (and a tiny fraction of that speed on the uplink side for arbitrary reasons) and somehow it costs upwards of $100/month. That has no rational correlation to reality in terms of cost to provide the service.

Massive enterprise systems are on a daily basis maintained by reletivlely small teams of specialists, most of who never have reason to physically touch a piece of gear. That happening in dynamic environment always looking for the next big step. An ISP has a comparativly simple task to direct traffic flows for the most part dictated by automated protocols.