TIL: Converting between USD and EUR is simple stuff. Just place the currency symbol at the end. No?
I don't find it that honest to require $39.72 from your customers that pays with EUR, and $29.99 from customers that pays with USD.
Steam does the same.
As well, know that as a EU buyer, if I buy from you in $, the VAT still applies.
See http://docs.recurly.com/vat for more information