I've had a couple of used cars that I bought for around 2 grand and "very good" is not how I would describe them. The used cars I got for 8 and 12 grand, on the other hand, were excellent investments. Those cheaper rides were sitting at over 200k miles and I can tell you there was a lot more than brakes and tires getting worn out. I shudder to consider the state of even a single owner vehicle with a million miles on it, nevermind a million automated taxi miles. That said, those little exceptions are a lot cheaper when leveraged on mass transit, batteries especially so in EVs.