Cost depends on what and how long it could possibly end up in the wonderful american crooked customs companies.
If you ship a container of cars, be sure absolutely everything is documented. I had an extra radio in the back of one car, and the exporter had used a set of wheels for dunnage in the 40ft container I had shipped over. Needless to say, a month later I finally got my stuff out of customs here in oregon.
I will probably not be shipping a container to the port of portland again though and opt for a better port in the future.
Also keep in mind damage that can occur wehn these cars are unloaded by idiots in a private company that is used for inspection. I lost a 1500 dollar bumper and there was nothing I could do about it.
I think I had 10 or 11000 into the shipping of the container after a month of customs hold up. Keep in mind I had to pay transport costs of the container, and storage fees for that entire time. I believe after it was all said and done the hold up in customs cost me about..... 5 or 6000 dollars. The shipping itself wasnt actually that bad.
Now roll on roll off should be a better bet, but again ensure there is absolutely nothing loose in the car.
You will be a % fee, I'd have to look at my paperwork, but I imported 3 lncer ex1800s and a minicab van, frankly I only had 6k or so into the cars so tax wasnt real bad. Most people wont be importing a bunch of cars though.
Frankly right now, I am looking into importing from canada, as I suspect it may be cheaper, and at least you can go up and inspect the cars. You will find old japanese cars often have a lot of rust.
1965 Debonair Deluxe, 88 starion,78 lancer, 84,85, and 86 ex1800 gsr turbo lancers,87 minicab van estate supercharged 4x4