No. Radar is not expensive at all. And the cost of lidar has also come way down. Several automakers are including a front lidar in their luxury brands for L2+ features. Cost is not the issue.
Camera vision provides rich information. In theory, camera vision can give you all the information you need to do full self-driving, assuming you have accurate and reliable camera vision of course. The information you get from lidar and radar, can also be obtained from camera vision. There is reason to believe that eventually (we don't know when), camera vision will be so good, that it will be able to do FSD without lidar or radar. So, I think the main reason Elon dislikes lidar/radar so much is simply that he does not believe they add enough benefit in the long term. He feels that you can do FSD without them, as soon as camera vision is good enough which it should be eventually, so why bother with extra sensors that will just give you the same information you already have. On the surface, that makes sense. There is a certain logic to it. But Elon is putting all his FSD eggs in the vision-only basket. If it works, it will be great. Tesla will have FSD for dirt cheap and super easy to scale. If it does not work, Tesla will be forced to add sensors to our cars.
The reason AV companies use lidar and radar is because there are conditions where camera vision will fail, where lidar and radar will not fail. For example, lidar works perfectly in total darkness where camera vision will deteriorate. And radar works great in dense fog, heavy rain and snow, where camera vision will deteriorate. So having lidar and radar provides extra reliability in different conditions. Lidar and radar work by bouncing a laser or radar signal off an object and measuring the time to come back. We know the speed of light, so we can calculate the distance very precisely. Lidar and radar can measure distance very precisely with less computing power. Camera vision can also get distance measurement but you have to extract the information by analyzing the image, which requires more computing power. Lidar can give you a very high resolution 3D "map". So with lidar, you can also classify objects, terrain etc... Radar can give you very accurate velocity of moving objects even in low visibility conditions. IMO, there is a benefit in having sensors that can give you valuable information like distance and velocity in more diverse conditions and don't require a lot of computing power.
Here is a video of Argo's new lidar. It basically gives the car incredibly accurate perception, even in total darkness:
Anyway, I tried to be fair to both sides. I hope that makes sense.
