A valid point, but also one thing to consider is the population. Passenger movements on the scale present in India can never be handled by Airways and neither can airports be provided everywhere. While I do wish to see High speed trains in India, I am skeptical about the execution of the proposed project, that too with such a large expenditure.
But, it is always better to invest in a next-generation infrastructure. The economy of scale you mentioned, will also hamper the introduction of such technology as in the future. The more, such an infrastructure upgrade is delayed, the more difficult it becomes to introduce it any time in the future. Even at the simple rolling stock/...
more...

locomotive/ signalling level, this is very much visible in IR. IR's network and operation continuously expanded for close to 30 years without any significant infrastructure updates or technology updates, because of which, now it is becoming very difficult to switch to a new technology. Just see the delay in the adoption of 3 phase locomotives and LHB coaches ( both of which arrived almost 20 years ago!). The sheer size of the existing operations mean that any kind of upgrade, even if it is beneficial, is very uneconomical in the short term. And in our country, where every politician is ready to pounce on such decisions ( harmful in the short term but useful in the long term), it becomes even more difficult to add any such enhancements.