I'm sure one of the experts will correct me, but I think that the cost of re-opening a mile of new railway is roughly in the ball park of ten million quid. Per mile.
We're not going to just re-open hundreds of miles of abandoned lines on the hunch that sometimes business cases aren't wholly accurate, just to check whether all of our surveys were wide of the mark.
You need something more serious than this, sorry.
...but, as I keep saying on such discussions, the Waverley line was re-opened as the price for the LibDems getting into coalition at Holyrood, not because it had an outstanding business case.
The LibDems used to have a loyal support in the Borders, so they ensured that Labour agreed to open the railway there - political hogtrading - rightly or wrongly - so to say that passenger numbers beat expectations is fairly meaningless because the line wasn't built on the basis of expected passenger numbers, it was built as the price of ensuring a functioning Government.
And, since it was a question of "the line must be built, regardless" (hence the clause forbidding any service to Gorebridge until the whole line to Tweedbank opened, leaving Midlothian commuters clogging up Edinburgh's roads, because the LibDems didn't want Labour to pull a fast one and only re-open through Labour seats), I don't think that much time was spent collating expected passenger numbers - why waste time forecasting demand when you know that you are going to go ahead and do it regardless.
By all means boast about the numbers but it's a phyric victory.
And it does get mentioned pretty regularly on these kind of threads, from the kind of people who know what they want and will then work backwards to try to come up with a reason for it.
Classic "Solution In Need Of A Problem" stuff.
You're probably best to - it's struggled to meet passenger forecasts and the frequency north of Mansfield was cut to reflect this (IIRC) - hence it not being brought out very often on such discussions.
Small towns don't require heavy rail though, do they?
I'm a rail enthusiast but not so blind that I'd suggest rail as the solution in every case - there are many other public transport options available - for the cost of one mile of railway you could order a fleet of buses and run them as a free service for many years - yet people always come back to suggesting rail as the only way of connecting places (and always obsess about the same disparate rural villages/ small towns).
If you don't understand that the cost of replacing/upgrading things that need to be replaced every few years anyway (staff uniforms, repainting stations etc) is relatively small and that spending five billion quid is a high price to connect a few rural villages/towns then I certainly agree that we should be on different forums!