Karim Hi Karim,
If you already have 3 cards (for Premium or Business), you will then need to pay a one-time fee of €9 for production costs. If you already have 4 cards for Joint, you will not be able to order the Travel Card.
Then when you activate the card, you will be charged an extra €3 per month on top of the monthly fee. If you block or freeze one of the cards, so that you have only 3 active cards in total, then you will not be charged the €3 monthly cost.
If you have less than 3 cards, then you can order the bunq Travel Card for no extra costs.
I have added this information the FAQ above, so thanks for the feedback. Let me know if you have any further questions!