The £4 per sector is not a credit card fee, it is a booking administration fee. Go on to ticketmaster to buy concert tickets and you are charged a booking administration fee for the tickets also, yes it's all done electronically and noone actually does any administration, but you are still charged it just like FR.
When booking a free ryanair flight it is actually costing you a negative amount. UK departure tax is £10 shorthall, so if you book a 1p flight and pay £4 booking fee (total £4.01) you are flying for negative -£5.99. Really it is the passenger who is responsible for APD (airport departure duty), so in theory the cheapest free flight you could get would be £10, as ryanair are paying your APD you are in fact paying a -ve number.
Get yourself an electron card and you can fly for -ve£9.99. I booked my sis and her hubby, my bro and his wife and my mate and his wife a day trip PIK-BVA-PIK all for a penny each way, total cost to me 12p on my electron card, they all thought I was a hero. Total cost to FR in APD? £120. Now all you tight asses, shut up about the booking fee or get yourself an electron card.here
https://www.halifax.co.uk/easycash/f...x&navigation=b