The point is that it's not worth doing even for cars. If the toll for the truck was $50, the proportional toll for the car would be one half of one cent.
On the other hand, trucks are often speed-restricted and the tax might need to be on the order of $50k for a 60-foot truck (which would still equate to around $50 for a car). The costs would be passed down to all of the things that trucks are used for, so I suppose the average person wouldn't really pay any less for combined transport+groceries+fuel+household goods, but it might incentivize the use of smaller trucks with lighter axle loads, but that would also mean more drivers/poorer fuel efficiency/more accidents per ton per mile. At the least we should be mindful of the way that motorists are providing a subsidy to the logistics industry (which we indirectly benefit from, as well).
It most certainly would not cost $50k for any size truck to travel down one road once, which is what matters if you're paying the cost to build infrastructure to track usage.
It might cost a semi truck $50k a year, but this also points in the direction of not tracking specific usage even for trucks: Just check the odometer during the annual inspection and then distribute the highway funds to states proportionate to estimated use.
Toll collection is stupid inefficient and privacy invasive.
Yes, obviously I was talking about an annual charge ("a tax") based on vehicle road wear; I don't think anyone had suggested that we charge a truck driver $50k for driving down one road, once. It's very common for the odomoters of heavy goods vehicles to be checked and for mileages to be logged regularly (this is probably a legal requirement in many cases, if not just a standard industry practice). I agree that toll collection would be unsuitable. My point was that charges for the use of large goods vehicles would need to be orders of magnitude higher than they are now, but that the charges for cars would still be sufficient to more than cover the cost of collection.
And if people wanted, the President of the National Cycling Federation could present the Secretary of Transportation with a $5 bill in an annual ceremony.
Dealing with government and taxes there is one additional factor to consider. The government can give tax cuts to targeted groups if they consider it beneficial to society.
So let say the truck has a $5000 tax to pay for yearly wear and tear on roads, but they also get a $5000 tax cut to reduce costs in the transportation sector. That will leave cars to still pay their road tax, even if in comparison they would be a tiny portion of the total road tax.
But if you want a general subsidy then you collect the money from a broad based tax like general income tax or sales tax, not low-efficiency road tolls.
