You should see RyanAir, you have to pay with their prepaid MC if you live in one of five countries, in all others, you need to pay with any prepaid MC, unless the flight arrives or departs from one of those five countries, whereupon you can't avoid the fee unless you have their prepaid MC even if you can't actually apply for it. Forget to print your boarding pass? €60. Cancel and want your taxes back, €20 for that. Luggage, from €15 to €40 for the first bag if you book it online, from €60 to €130 if booked by telephone or at the airport. €35 to €50 for the second bag (15kg max) or €105 to €150 at the airport. Oh and excess luggage by the kilo... €20.
So you can get a ticket for €16, but you can't actually ever really pay €16 for the ticket.
They charge €2 for pay for force majeure charges, in case of flight delays that they have to compensate people for. €0.25 to pay for the carbon taxes. They used to charge a fee for not being handicapped. And they charge €1.50 to €2.50 for them to text you reminders about your flights..