That's fine. We don't have to agree, it's a discussion forum

In brief, it's doesn't have to be a 250mph railway with all of the attendant extra costs in civil engineering, land take, tunnelling, energy use during operation, high speed stock etc.
And before you glibly say a slower railway wouldn't be any cheaper, it would. Otherwise reopenings such as the line to Galashields (which needed new bridges etc and a lot of formation rebuilding so is almost new build given 50 or so years of dereliction post closure) would have come with similar per mile costs to HS2