Larger size, larger engine, more natural resources required (and more pollution).

Also, not only you need to account for the negative externalities, but you also need to provide a disincentive for purchase, which then needs to be progressive due to the decreasing marginal personal utility.

Those aren't aspects of just luxury cars...and they're aspects that I covered in my previous post.

> but you also need to provide a disincentive for purchase

You need to pay for the externalities. Beyond that, I disagree that you need to disincentivize the purchase.