Tesla could do this, because at initial strges, they relied on Lidar, Radar and other high precision, specialized sensors, because they were used for mapping the terrain. After millions miles driven, these sensors no longer need to serve their mapping purpose, because the areas have already been mapped & safe passages have been created. Just like a real, experienced driver, who knows the roads, all they need are Motion Sensors, GPS for correction & depth sensing color cameras, for handling infrequent dynamic scenarios.