I just bought a ticket at KLM.COM and they charged me 125 CZK ($6,2) for paying with my credit card. When I went to Airfrance.com, they wanted to charge me 250 CZK, which is double than KLM. They both have an option to do the bank transfer, which is free. So you can see you can see these charges elsewhere, even in less likely companies than is Vueling.