In my experience you can expect to pay an extra $10-20 for an import game. I've heard many different explainations as to why, but the one which makes the most sense is that Japan's economy is weaker than our own. 1 yen is worth a lot less than 1 U.S. dollar, and so companies selling things in Japan have to jack up the price to make a profit, where as in the U.S. companies can make the same (if not a larger) profit from a cheaper pricepoint.