But still what? How many gas engines and transmissions in comparable luxury cars will last 8+ years without significant cost? The Tesla warranty is 8 years but the batteries will last significantly longer they will just have less than 80% of max storage (I believe that is the warranty threshold).

The tesla powertrain as a whole should last a million miles or maybe more with nothing more than routine maintenance and some battery pack changes which will drop in cost over time. If battery pack changes get down to $5K (which seems very possible), and battery packs are usable for let's say 150K miles, then you get a car with a power train that runs for a million miles for about $45K in maintenance (add a bit more for tires and other incidentals) and then subtract the cheaper electric fuel cost. This is less than the cost to keep the power train running for a Mercedes S class for one million miles (which will probably require 4 or 5 transmissions and 4 or 5 motors to get to a million miles).

But realistically people don't repair 150K+ mile S classes because it would cost $30-40K to replace the tranny/engine plus all the other engine things while the car would be worth very little, so they junk it and buy a new car which means the cost of owning an S class for one million miles is more realistically the cost of owning 5 or 6 S classes.