The population along the whole Melbourne-Brisbane route is 15 million people and growing.
By the time the HSR is built, expect the population to double.
Melbourne - Sydney is one of the highest demand for plane routes and will suffer.
Also, planes skip over the regional towns in between.
Also, we have progressively upgraded the highway, and how much did that cost?
How much did it cost to turn the Hume Highway to a Freeway and how long did it take?
If we thought it was just too expensive and too hard, maybe we would have kept the highway btw Melbourne to Sydney as it once was.
Yes, there are many short-medium term projects with higher benefits at the moment, but in the longer term, the benefit of HSR will be there for the next 50 years when the population grows further.
The priorities are correct, the opposition is planning to spend many on short-medium term projects like the Metro Tunnel, like the Metro Net plan, like the Cross-River Rail project. And also spending 100 billion dollars on a mega project, doesn't mean smaller regional rail projects are neglected, it's complementary.
If the trains from Melbourne to Sydney are one dedicated track, that would mean the existing track capacity can be used for other uses. Also would boost productivity from regional centers.
The population density in our cities is increasing and the traditional high-speed rail technology is starting to become more affordable, it's the right time to plan it for the future.
Yes if the business case states that it's unfeasible in the next 10 years and put the project on hold, then that's alright. But there will be a point of time, where it will be feasible and useful for those along the east coast.
As for connecting up from Melbourne - Perth, air-travel would always be a win vs HSR. But for Melbourne to Sydney, it's becoming more feasible as time goes on, making the dream of HSR very possible for future generations.