Depends on which ones you buy and when.

How much does it cost to replace an EV battery on average?

It's very easy to look at 10+ year old batteries and extrapolate.

There aren't a ton of 10+ year old EVs is my problem. 10 years ago EV were still a pretty niche thing. If you have that kind of info I'd love to take a look though.

That's what we call a "loaded question". There's all kinds of companies.

I definitely wouldn't call that a loaded question. How do you figure that it is?