> I don't have a source for the detailed cost breakdown, but I can imagine the majority of the cost is labor and digging up/filling the road since the sensor itself should be less than a thousand.
Those are installed with a massive handtruck saw while cutting off a lane of traffic all day. It takes a half dozen people working on-and-off, doing different jobs. It takes jackhammers, high pressure water from a tanker truck, and people to place and wire the sensor to power. It's way more complicated than anything you'd do at scale, because it's infrequent and the goal is to do it thoroughly with non-specialists.
If you were installing millions of tags you'd have a dry drill that could go off the back of a truck and place+fill a tag in ten minutes. If you had a line you'd have a it hanging off the back of a truck and place it continuously, like a street cleaner or edge clearer. For tags there's no reason they'd need more than one person to place and no reason to even put them in the road when they could just go on the edges. Triangulate with directional antennas or something.
That said, I think it's pretty obvious that locating the roads is by far the easiest problem for self driving. If you wanted to make a serious attempt you'd want every car to broadcast a short range location, and to share data over a mesh network. "Knowing where the road is" to precision RFID would give you has been solved for over a decade with GPS and digital maps.
Much more pressing issues are non-obvious sensing like hearing a car around a blind corner or knowing when to be cautious about moving. Knowing when something is coming onto the road or when a vehicle is having a problem. Inter-vehicle communication is just so obviously important to that... it's really frustrating how vaguely it gets talked about. I don't give a shit about teslas coordinating braking so they can form a tailgate train for efficiency, I want cars of all kinds to be warning each other about what they intend to do. I worry that legislation or at least a regulatory body will be the only way to even get people talking about it seriously.
Other than that, cameras watching for intrusion into a road would be easier than solving it from vehicles. It seems patently ridiculous putting cameras to watch every 50' section of road. 1080p+ cameras, simple detection, and mesh wifi can be built in a $30 package... but there are >2.5 million miles of paved roads in the US. 30$ per 50' would cost, bare minimum (and ignoring electricity requirements+labor+the pole to put the cameras on) 8 billion dollars.
