The cost to replace a Model Y battery is around $13K (no where near 50% of the cost of the vehicle). More than that, the battery will probably outlast the lifetime of the vehicle, with a design lifespan of approximately 500K miles.
Yes, eventually when the battery dies it won't be repaired as such - instead it is designed to be nearly 100% recyclable.
https://www.youtube.com/watch?v=T7Q0nNkQTCo
Here's where right to repair is exceedingly important. Obviously if it were up to Tesla, you'd only be allowed to go to them for repairs, at their full markup. But here's the secret - they have a huge markup, but no monopoly on electrical engineering. Like the video shows, 3rd party repair shops can repair these things. It's not rocket science - you're thinking of a Elon Musk's other company, SpaceX.
But $5,000, down from $22,500, is still more than "a couple hundred bucks to hundred bucks to tear the car down and expose the battery, and then identity the bad cell and pop in a new one". Now, in my haste, I wrote "cell" when I mean "module", sorry about that. The car for which I'm referring to that job is at the bottom of the segment - a first generation Nissan Leaf. They first came out in 2010 and here's a 12 year old used one for $6k (https://losangeles.craigslist.org/wst/ctd/d/redondo-beach-20...). It's almost guaranteed to have at least one bad module if you're buying something that particular car (they didn't have battery cooling systems that generation) and that old (simply due to the number of charge cycles).
The procedure for finding the and replacing the bad module is documented at:
https://www.youtube.com/watch?v=FTiFEapky8s&t=24s
and
https://www.youtube.com/watch?v=TVaCMbXKrd4&t=423s
For the module itself, you're looking at 3rd party supplier for a refurbished one. Here's one battery module for $90 on Ebay https://www.ebay.com/itm/354422211418?hash=item528535c35a:g:...
or another listing asking $250: https://www.ebay.com/itm/225422969988?hash=item347c418c84:g:...
Or via FB Marketplace for $60: https://www.facebook.com/marketplace/item/5165480583467846/
If you take your Nissan Leaf to a shop that specializes in them, they'll likely have modules for cheap off salvaged cars, but we don't have access to those prices here. So let's say a refurbished battery module is anywhere from $60-250 and then kick $200 in labor to your cousin who's good with cars to watch those two videos and replace the bad module for you unless you're that cousin, then spend $250 on a battery module and buy yourself a nice voltmeter.
Official battery replacement jobs on a Nissan Leaf are going to run you much more (multiple thousands) but if you have a Nissan Leaf, or any electric car really, you should be aware that that's a total ripoff. Everyone knows you don't go to the dealer for repairs on an ICE unless you want to get ripped off, and the same is true for EVs.
Obviously there's some batteries that are tolerant of this (Prius' commonly have this repair on their NiMH batteries), but it's not universal.
Similar to many Apple or Xbox repairs, they swap it for one they've previously refurbed and tested, then add yours to the pile to be refurbed for another customer rather than make you wait for your specific battery to go through the process.
This sounds great, for which EVs is this available?
"For many electric vehicles, there is no way to repair or assess even slightly damaged battery packs after accidents [..] Battery packs can cost tens of thousands of dollars and represent up to 50% of an EV's price tag, often making it uneconomical to replace them.
While some automakers like Ford Motor Co (F.N) and General Motors Co (GM.N) said they have made battery packs easier to repair, Tesla Inc (TSLA.O) has taken the opposite tack with its Texas-built Model Y, whose new structural battery pack has been described by experts as having 'zero repairability.'"[0]
https://www.reuters.com/business/autos-transportation/scratc...