You're not kidding there.
Check this price list:
Building a road in Florida.
It's a little cheaper in Kansas (I couldn't find such a nice price list), but calculating the budget on a dozen projects this year from the paper, this list is pretty close to accurate. That is to say, devastatingly expensive.
Like a waterworks, it doesn't matter how few people use it, age happens. A fifty year old road that's never been battered by more than Prius farts will still need rebuilding. The interstates around here? Seems like every fifth year or so.
I compared the traffic counts for some roads around here and amortized for a guess of how long they'd last before next repair. Came up with numbers between 10 to 20 cents per mile per vehicle driving down the road. At 42.4 cents gas tax per gallon (a dime more for diesel), that's less than even semis (at 5-8 mpg) are paying, let alone me in a Corolla paying less than 1.4 cents per mile. This is before visitor centers and heritage trolleys and bridges to nowhere. If the fleet average mpg goes up, the gaping budget hole will get even worse. And EVs? A different method of paying for driving privilege will have to come out.
So, yes, another piece of our infrastructure that won't withstand conservation.
At 1% annual growth, human bodies will incorporate every gram in the observable universe in approximately 10,170 years.