With used parts, for example R34 wheels vary in price. The reason for this is some have more scratches then others and the same goes for other used parts. If the Aus dollar drops against the yen then of course you can expect to pay more for your parts. ( "prices vary so much" ) Anyway you slice it if the dollar is low you won`t be too much out of pocket . If the Aus becomes too weak against the yen then I buy my new parts in bulk quanties, Hence I receive parts cheaper and so to does the customer. Anothor point is that these currency converters don`t exchange your funds, the banks do and they will always give you 2 to 3 cents less per $ than the currency exchange rate. Credit card companies make up their own rate + 3% on the total order. I don`t make up prices as I go along I just work of the bank exchange rate. If at times I have made a mistake on pricing, then by all means challange me on it.