That is a good question. Automobiles impose costs on society and therefore should be taxed at a punitive rate to discourage excessive use. Here in Singapore the costs of purchasing a Honda Civic are in the neighborhood of USD$150,000. Part of this is tax. All cars are taxed at 200%. There is also purchase of entitlement to own an automobile (~$30,000).  There is also purchase of the entitlement to drive which is about $20,000 per year if you want to be able to drive during peak hours (much cheaper for an off peak license).

These are excellent moves. Cars cause external harm and therefore call for punitive taxation.

Guns should also be heavily taxed (e.g. there is one paper which suggests that $600/gun is an appropriate tax rate).