throwing money at the NYC subway seems to have a generally great track record (albeit one featuring less efficiency than throwing money at other global subway systems). NYC could not function without it.
The 7 line extension cost over $3 billion dollars in 2023 terms to build 1.5 miles of track from Times Sq to Hudson Yards and build one new station there. I defy anyone to conclude this represented good value.
The NYC transit system costs $20BN/year to operate, serves a population of almost 9M people and pre pandemic had nearly 10 million passenger trips a day; currently 5M.
Montana spends $1BN/year on roadways and receives another $3BN/year in federal funding and serves a population of 1M people.
The NYC subways system moves five times the population of Montana every day and costs half as much per capita.
Subways are not a waste of money: throwing money at the NYC subway system under the current set of parameters is a waste of money.
P.S. you're also comparing apples and oranges; you're only looking at the MTA operating budget; not the operating + capital budget which the Montana numbers represent.
It was probably good value for anyone that owned any surrounding property.
Ideally the increase in property value should be captured by the public who made the investment - self funding effectively. But that's just the old LVT argument.