JulietNovemberPapa, it doesn't matter whether people book a single or return trip as the charge is applied per sector so your illustration is fairly accurate. Yes ancillary revenue is the key to airlines surviving in the current economic climate but the problem is that paying for your flight is part of the booking process, not something optional!
While I had no issues with any of Ryanair's other charges and whether they are advertised or not, this is one that is pushing my tolerances a bit. I have no real sympathy for people with excess luggage or if people wish to pay to have priority boarding that's all fine - these are issues where the choice of payment is completely within the control of the passenger. An Electron card however is not always easily accessable depending on which country you live in and in some circumstances will make the debit/credit card fee mandatory to passengers.