Quoting to expand on a couple of things....
If you buy a 2012 for say $20k or so and immediately after the 8-year warranty expires the battery pack poops the bed. The odds of this are very slim but let's just pretend for the purpose of this exercise. You can source a used battery pack for $10-$15k or so (these price will continue going down as supply increases over time) and then you're into the car for about $30-$35k. My guess is had you bought even a 2-year newer car with half the miles you would have paid much, much more. So you're already money ahead and there's really nothing major on these cars that can fail other than that so you're going to be money-ahead the longer you own the car.
People are down on Teslas with miles but look at the price gap to see why it makes sense to buy one of these with miles or nearing the end of warranty. I've seen the same used Model S cars with a price difference of $40k+ and the ONLY difference is miles. That's a substantial difference on the front-end & doesn't even factor in the rate of depreciation over period of ownership which will be much higher on the more expensive car. You can buy several battery packs for the savings and you're still money ahead and for every battery pack you don't have to buy you're even further ahead... if that makes sense the way I stated it.
Another way to look at it is you can drop $70k or so for the exact same car with ultra low miles and after you get it to the same miles as a higher mile one that's currently selling for $20k you're now sitting on a vehicle that depreciated $50k to have a battery pack in warranty. That $50k will buy a LOT of battery packs.
IMO the math is skewed in a massive way right now to buying these things used and rolling the dice. I personally don't think it's a bad gamble at all but even if you have a massive failure you're still money ahead over buying a new one and losing $100k in depreciation over 5 years. $20k in annual depreciation is a large sum of money to pay for "peace of mind" on the worlds most reliable vehicle type IMHO.
This actually reminds me of my new/used car sales days in the late 90's when people would come in, buy a brand new Dodge truck and pay about $20k premium for the diesel option making the truck nearly $70k total (it's been a while so my recollection may be a bit off on those but the point remains so stick with me here....). The same customer would then come in with about 50k on the odometer two years later and trade it in for about half of what they paid losing $35k over two years. Not only did they lose their a$$ on depreciation but they invested a LOT of money for an option that would increase the overall life span dramatically. So why invest more money on the front end if you're not going to take advantage of the primary reason you invested the money in the first place? I feel like we're there right now with EVs where a lot of people who are used to driving $150k+ Mercedes have been buying new Teslas so that's what they base their "high mileage" opinion on which is the polar opposite of EVs.
Also, regarding your 12v battery statement, Tesla will cover the 12v battery under warranty in most cases that I've read about. I even experienced this first-hand in our 2013 CPO (that's currently for sale) a few months ago. I assumed I'd need to go to the store to buy a new battery and replace it myself since most manufacturers consider this a wear item like brake pads and don't cover them under warranty. I did a little research online and discovered that Tesla was different in this respect so I went ahead and scheduled service. I confirmed it was covered under warranty at no cost, they come and replaced it and my invoice confirmed the $0 charge. Now, this could be just a good faith type situation so YMMV but from what I've read this appears to be quite common. Still not worth paying $150k though IMO.