There is no handling charge, no processing fee and no percentage added for the privilege of settling your invoice. Pay by iDEAL, by Bancontact or by bank transfer and the amount that leaves your account is the amount on the invoice.
There is exactly one exception, and it is a card that costs us money to accept. Cards issued outside the European Union, and business cards wherever they come from, are charged to us at a materially higher rate than an ordinary European consumer card. Rather than fold that into everybody's buyer fee, we pass it on to the people it applies to.
It is decided by the card, not by your address — a European member paying with a card issued elsewhere will see it, and it is shown on the card in your account and again at checkout before you confirm. If you would rather not pay it, a bank transfer is always available and always free.