Its not really that much more expensive to do quad track than double track, slightly larger supports and more wires but the cost planning, of installing the bases and the manpower is still the same. Great Western Electrification (which only includes one route through Bristol and some of the works being done for Crossrail anyway) was budgeted at £1bn, I make it roughly 150-175km. The Lancashire Triangle Manchester-Liverpool, Manchester-Chorley, Preston-Blackpool and Liverpool-Wigan I make just over 100km roughly and was budgeted at £300m. There are some major differences such as no new connections to the National grid or transformer stations being required in Lancashire, each connection to the national grid for example costs £20m a pop. When you start talking about electrifying the whole network you dont get those kind of savings from using existing infrastructure capacity, you need to keep building the transformer stations even though their in the middle of nowhere and hardly any trains use the line.
The Great Western signalling renewals London to Bristol have been budgeted around £1bn on their own, the South Wales section resignalling including heads of the valleys cost £400m but wasnt ERTMS like GWML will be. The Cambrian line being signalled with ERTMS cost £60m and thats only a frequency of 0.5tph though lengthy at 215km of actual track with 19 trains (3 NR test trains) fitted with the equipment, more will be fitted this year.
