Is that likely to change with self install though? As there's no engineer visit, so less money to recoup.
The money they need to recoup is on at a minimum:
The green cab
The DSLAM installed in the green cab
The fibre to connect up the green cab
The kit in the exchange the fibre connects back to
The engineering for all of this to be put in
This is not cheap. The engineer visit is a minute part of it which the ISP already pays or passes down to the customer.