When I asked on the 21st of August that I would make a payment of 215 dollars, I was told that it was calculated on a site that showed the current exchange rate.
Coming to today, when I come to the payment screen for 5772 Turkish liras with the current exchange rate of 215 dollars, I am asked for 6075 Turkish liras, i.e. 226 dollars.
Most payment transactions processors base upon the rate at the moment of the transaction. They also frequently charge an additional processing fee for the exchange, and each payment processor will charge various amounts. That's why there is no way for anyone to tell you now what it would cost you if you purchased now or tomorrow... but you can almost guarantee that looking at the downward spiral of the lira against the dollar, the longer you wait, the more expensive in your native currency it will be.