I believe a new battery can be had for roughly $5000 to $8000. I doubt you'll find a barn find that you end up putting less than that in really. Plus, I don't think barn finds are really a thing; I just mean I know it happens, but it has to be less than 1% of car purchases.
@Xtinct the rest of this isn't a reply to you, I just have to bow out of this thread. There is so much misinformation and unnecessary hostility in this thread it is crazy. I don't know why people get so worked up about electric vehicles. They are awesome for what they are awesome at, which isn't everything. It is a fact they are being pushed on us, so you can either get grumpy and believe bits and pieces of information that align with what you want to be true or research both sides.
I recommend the Engineering Explained channel on Youtube. He has a ton of videos on what works about them and what doesn't, including the grid (spoiler alert, it can handle it). He is very balanced. He loves cars and has a supercharged Miata and a Tesla.