Well I use that train everyday, and would say that more than a handful alight at Saltash with quite a few boarding. The stop does not cost ^100, I suspect that figure is for a stop/restart from say 80-100mph. As the linespeed at this point is just 15mph, the fuel cost and probably more importantly the time cost is much less.
Maybe for Saltash but what about St Germans?
Isn't St Germans approach speed severely limited by the viaduct ?
I hate using the 17:25 service as it dawdles through Cornwall, taking the 17:55 is generally just as bad as it is often held up by the 17:25 sometimes as early as Liskeard then St Austell, Truro, Redruth and most frustratingly at Penponds.
Both services are quite good at missing the St Ives branch.
Flippin annoying when I've been travelling for 8 hours to get in a couple of hours birdwatching in Devon.