http://blog.caranddriver.com/feds-watching-fords-run-around-...
However I'd challenge that this is a market failure - this is an example of the failure of a rules-based approach to regulation.
In countries which take a principles-based approach to regulation then the substance of the transation is considered as well as the form.
So this kind of nit-picking to circumnavigate the rules wouldn't have been allowed.
Considering the substance of the transaction isn't a viable strategy, it might be possible at larger scales as in your Ford example, but individuals can and will find clever ways around tariffs that are impossible for the authorities to keep up with.
As an example, I lived in a European country where import tolls on bicycles were much higher than the import fees on spare parts, so if the price of shipping was low enough you could simply ask the seller to send over a bike in multiple packages marked as spare parts to evade the import fees.
How are you going to detect cases like that with perfect accuracy? You'd need some massive tracking system to figure out who bought what, and even then it could be trivially evaded by me and a friend buying 1/2 of two bikes each as spare parts and combining them after they've been imported.
You think nobody tried to undervalue taxed imports yet? Probably a fraud as old as mercantilism.
Nobody's trying to undervalue the car as costing €1,000 with a €10,000 stereo, that would be fraud.
The point is that by introducing differences in what sort of taxes you have to pay for certain products you trivially open yourself up to legal tax evasion in the form of simply bundling higher cost items as part of products in lower tax categories.
Perhaps a better example: Let's say you have a 200% tax on cylindrical metal tubes, but a 10% tax on bicycles. A lot of people would now legally import bicycle frames, cut them apart, and evade the import fees without the authorities being able to do anything about it. There's nothing illegal about buying a bicycle frame, and there's nothing illegal about cutting apart your bicycle and re-using it for parts.
I think OP did not mean "put 0 tax on cars" but rather remove the extra 100% tax on cars, so it's just taxed like any other product - i.e. just the same as tax on audio equipment. Then it would not matter.
E.g. if the purchase of cars isn't taxed I'll just import €10,000 of audio equipment by buying an old beater, then ripping out and selling the sound system and selling the car for scrap, while making a big profit because I'll be competing with local sellers that have to pay import tax on sound systems.