The question isn't _new_ runs of fiber vs coax, everyone just runs fiber for that. It's the cost of upgrading existing runs. HFC (hybrid fiber coax) networks have been the norm for a long time. When the original coax was run it was significantly cheaper to run it even accounting for inflation. Like all major construction projects (which is what a coax replacement is) costs in the US are spiraling upwards: https://www.bloomberg.com/news/articles/2021-12-08/why-build...