Absolutely correct. But also there could be other reasons. The Mercedes cars offer SAE Level 3 certification ("you are officially not driving the car or watching the road, but we may demand you take over"), versus the much more dangerous Tesla Level 2 ("you are still responsible for driving and must constantly supervise but also the car will be doing it all for you, please don't stop paying attention at any point").

There have been, what, more than 50 self-driving fatalities in Teslas already? Of course the insurance premium would be higher.