Here's the thing: The Model 3 is still a car. And it's a techy complicated one, so there are actually many failure points.
If you're familiar with things needing attention like ball joints, cabin air filters, coolant changes, brake service, replacing headlights, dealing with rust, etc. on other modern cars,
these things will happen on the Model 3 as well. You may additionally need to give attention to more unique things like electronic door latches, the middle screen, electric HVAC components, and so on. I expect that outside the 4 year warranty (only the driveline is 8 years), there will be many such bits that require attention over time.
Only the internal combustion engine and associated transmission have been removed. In some ways, great. In some ways, not so -- we've darn near perfected such engines over decades at this point, and million mile gas engines already exist with the appropriate (not necessarily costly) preventative maintenance. The electric drive units can and do fail. The battery packs can and do fail. Unlike the much more generous older Model S/X warranties, we're on our own for these major components after 8 years or 192,000km (120,000 miles). Keep in mind the high mileage Model S/X vehicles out there have usually had both multiple drive units and battery pack replacements already, and the Model 3 batteries are new and untested in the long run.
Other parts are generally cheap for the Model 3. Once the out of warranty market starts to gain traction for this vehicle, it will be very interesting.
EDIT: A very important note. Some other manufacturers also offer extended warranties specific to the drivetrain, but they stop short of "expected life" as well. In the case of a gas engine or transmission, you can do a lot to fix and replace pieces without replacing the whole engine/transmission. In Tesla's case where the warranty also doesn't cover the full "expected lifetime", the major components are significantly less serviceable (part by part) than a gas engine. And if an individual part can be addressed, you
may need to take it to Tesla and pay high first party labour rates, which is not necessarily true of gas engines.
Tesla would not give a warranty for 8 years if the battery was going to fail before the 8 years. BMW has the same 8 years on their BMW i3.
Are you going to travel 500,000 miles in 8 years it's more like 16 years if you travel 30,000 miles a year. I'll only travel 10,000 miles a year so thats 50 years and I'll be well worn out and not able to drive well before.
The main cost will be tires which every vehicle has.
There have absolutely been battery failures with the Model 3. The warranty is also 120,000 miles
or 8 years, whichever comes first. That's also for the LR. The SR+ is 100,000 miles. I will reach the distance limit around 5 years of ownership. The battery also won't last 50 years -- batteries degrade with time as well.
