Not even just the battery (although that probably is the biggest one), but maintenance in general.

If I buy a 5 year old Corolla with 50k miles on the clock, I have a pretty good idea of what maintenance is going to like for the next decade, and I know a mechanic who can do the work.

I have no idea at all what will happen with a comparable Tesla over 10 years.

Nothing, because electric cars have basically nothing to service. They don't use oil, they don't have timing belts. It's a battery and wheels.

Everyone likes to focus on the battery, but in my experience with Ford, Honda and Nissan, there's more frequent expensive surprises in gas engine sedans.

Replacing the passenger occupant detection sensor for the airbag system in my 2007 Ford Fusion cost $2K. After a series of other issues with things like the transmission and fuel injector, I ultimately traded it in for $500.

I got a used Nissan Leaf with low mileage for $18K a few years ago and haven't taken it in for anything yet. Battery health is still at 90%, and I could get that replaced for around $6K if I needed to.

I feel a palpable sense of relief that the surprise maintenance bills have stopped.