You are right - Rail freight is extremely expensive (typically more expensive than road except for very long routes) and cargo bikes have a tiny payload.
Think about container ships - massive vehicle and much lower cost vs rail freight (dependent on distance).
What matters is large volume per ride, which trains can definitely pull off.
Additionally, a train always costs the same amount to run, no matter the number of passengers, so in countries where trains don't see much use (like the US), they'll be much more expensive than they should be.
If you look at how DB sells the vast majority of their tickets (Sparpreis and Super Sparpreis) in the 9,90 / 14,90 to 49,90 price range (including for 1000km long distance journeys), train travel can be relatively affordable (but obviously still more expensive than car travel if you travel short journeys, fill the car with 7 adults and don't include the road maintenance paid for by regular taxes)
If you are flexible and plan ahead. If I decide now to go visit my sister tomorrow (~4 hours by the fastest train route), want to get there not much slower than by car, and travel at a time that is convenient for me, then I'll end up paying a lot more if I go by train, even if I'm traveling alone.
I’ve never owned a car, and stopped during the middle of my driving lessons because I didn’t see the purpose in it. That was 10 years ago, and I’ve moved halfway across the country, traveled a lot, never had a car, and overall I spend significantly less on travel than the friends who do own cars (while traveling more comfortably)
The FHWA is handing out $52B in FY22. Now, you might say, oh, well, more people drive, so the FHWA is clearly a more sensible place to invest. But Americans spent $743B on their cars, including payments, interest, and insurance.
It's a scam.
The northeast corridor, which is basically the only Amtrak route that is actually focused on being a useful route for passengers, runs at a profit.
Have you factored in all the costs associated with owning a vehicle (e.g. cost of purchase, maintenance, etc)?
That sounds intuitive to me but the fact that train tickets are so expensive on long distances (more than twice than if you travel alone in a car) makes me think it's not the case.