With limited space on the pavements and a requirement to get planning permission and get residence input for the placement of every single green box I can see how FTTC can appear to be cheaper and then once the council gets involved and the residents all don't want the box in front of their house in the end your reached customer base drops in reality and breaks your cost graph.
Recently I have lived in 3 places all with FTTC, not one of those places could I actually get it. The local residents all protested against the box and it never got installed, the end result is that actually whole roads are not getting even one box let alone the several this technology would require. While us techies will happily have a green box outside our house if it means 10 gbit/s internet grandma next door wont allow it on the street and so the council wont let it be installed. I suspect BT in the UK is having this problem a lot, its the reason the regulator has now asked them to go beyond just postcode rollout details but the truth is that a lot less than the anticipated homes are actually ending up with access to it.
I can't see an even higher density working out generally. The boxes on the street are a big problem here, many communities just don't want them. FTTH is a lot neater, it might cost more but its penetration would be dramatically higher and require less planning permission applications.