My theory is that they are getting out off Fiber / ISP business not because of costs, but rather the goal of Google Fiber has been met. Back in 2012 there was a real risk posed by ISPs, however with effective lobbying ensured Net-Neutrality becoming adopted as an official policy, and with next president likely being from the same party. There is no longer need for Google Fiber as it was in 2012. Also maybe there is another technology thats more lucrative which is on horizon and thus Google is recusing itself from making likely to fall investments in optical fiber network.