Hans Vestberg of Verizon is passing 30M homes without raising capex.
NTT DOCOMO's very respected CTO Seizo Inoe in 2016 called high costs of 5G "a myth" in presentations at the Brooklyn 5G Summit and an IEEE conference in Kuala Lampur. He pointed out that LTE was cheaper than 3G and that much of the 5G would use existing towers and backhaul.
Vestberg, former Ericsson CEO now running Verizon's network, sees mmWave costing $200-400/home passed as they deploy to a quarter of the U.S. (Obviously, some other areas will be more expensive.) He just told a CITI investor conference 5G is
"Massively, massively cheaper than having a fiber all the way to the home to have sort of a beam in the air going to the home."
Verizon has previously said their costs to pass a home with fiber were $700 in 2007 and went down from there, presumably to $400-600. AT&T has confirmed similar as they deploy 15M lines of fiber home. I'm inferring that "massively, massively cheaper" would be $200-$400.