Yes, our booking system is based on EUR and unfortuantely it can only handle one currency. When your local currency is different, then the conversion will be done based on your card provider/bank rates. When you have a special card, like Curve, Revolut, then the system may charge the EUR sums direct.
Cash payment is only possible on the boat, before departure (as long as there are empty seats left), tickets purchased on the boat costs EUR 10 or HUF 3500.