I have been in the used vehicle business on and off for the last 30 years. Much of the advice given in this thread is correct, but a whole lot of it is not. First, where you buy your bike is irrelevant with regards to taxes and registration. You can buy a bike where the market is cheaper (east coast) get a temporary transit tag and ride it to wherever it is free and easy to register. if you are coming from Europe, the east coast is cheaper to fly to and from Australia and Asia, the west coast is. Bikes in colder climates are ridden only during riding season and will have less miles.Many states do not require insurance to register, you can take your chances to save money.

All countries in the Americas will let you enter with a registration. Most titles don't show plate #s so a Reg is better anyway.

I am in NY and can help anyone who needs to buy a bike here and can get temp plates so you can ride out west to register.

You don't pay tax when you by a bike, only when you register it, unless you are buying from a dealer and registering in the same state as the dealer is located in. I bought my V-strom new in NY but since I was registering in TN, i paid no tax to the dealer.

I have been selling cars on Ebay to people all over the US and Canada since the dawn of the internet, I am happy do answer any questions regarding buying inthe U.S.