Peak Internet growth may have been a couple of years ago. For more than a decade, Internet traffic went up ~40% every year. Cisco's VNI, the most accurate numbers available, sees growth this year down to 27% on landlines and falling to 15-20% many places over the next few years. (Chart below) (Thank you, Arielle)
The result: bandwidth cost per month per subscriber will continue flat to down. For large carriers, that's been about $1/month since ~2003. Moore's Law has been reducing equipment costs at a similar rate. This is confirmed by the global carrier spending on service provider routers, which continues about flat per customer.
Mobile growth is staying higher. 40-50% worldwide. Fortunately, mobile technology is moving even faster. With today's level of capex, LTE networks can increase capacity 10x to 15x.