I just realized I have a 2nd data point. I'm currently considering adding a new Shelby GT350 to my garage. After the test drive, the dealer offered me low $50s for my grigio '98 355, 29k miles. Not that I'm considering it, he also gave me a trade-in value for my Boxster, but he was for real and trying hard to get me to close a deal on the Shelby when I said out loud I don't need 3 cars. The tax advantage in NYC would have been +.08875, which all-in on a trade I didn't think was too bad.