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I don't know if it works for Tesla cars, but the website www.iseecars.com has a tab labeled "VIN Lookup" that provides details of cars for sale including the date(s) that they've been listed for sale, any price changes and other useful information. It may work for Tesla cars, but if Tesla keeps information about cars for sale private the website will be unable to pull the needed data. Still, it's a good site for any car that you may be researching.
Why would Tesla share how long the car has been listed for. You might use this to try to get the price lower. And usually with Tesla, the price is the price.