I went through a detailed estimate of the cost of the 21" wheels over the lifetime of the Model S. My entire blog post can be found here: 19 Tesla Owner In summary: 1. For my driving conditions, the 21" wheels will cost a total of 8.3K more than the 19" wheels over 15 years. 2. Tires are recycled or reused about 80% of the time, so I can feel okay about buying a few more tires. 3. The replacement costs of the Model S 21" tires will be less than the Roadster because the tires are cheaper and also the low mode of regenerative braking. 4. The 19" tires will only last 50% longer than the 21" tires. In the end, I changed my order from 19" to 21" wheels. I know these estimates are really just guesses but as reasonably accurate as I could make them. I did forget one item on my original blog post. Eventually the 19" wheels will show some aging through the wheel itself. I didn't look into this issue much but my Tesla representative did mention this fact.