If you are paying via Credit Card, you should ask your card center to give you an indicative rate for the payment FX rate for EUR; Hika will only charge you in EUR to your card and the FX is happening with your card center EUR > USD.
If you are paying via Paypal, there is a FX indicator in their control panel, you can check the indicative Payment and Transfer FX rate for respective currencies. Hika will only charge you in EUR only.
Note: Since the credit card / Paypal payment may not happen in the same day of your purchase, FX rates are still subject to change due to time.
(I am not a staff) but someone who familiar with this.