Hi Bacardi, welcome to the madhouse (or forum if you prefer).
As I'm currently a UK citizen I've purchased on here, but I don't recall there ever being an exchange rate listed or anything like that. Whenever I'm about to buy anything with a substantial price, I always visit xe.com first to check the current exchange rate, make sure it's not currently on some huge hump. You can even go back in time to see how the trend is going and time your purchase like that if you wanted. There's never any guarantee how it will go, but at least it might give you an idea of how much you'll be charged in total.