I enquired with my bank (Nationwide) as to why some companies (such as Ryanair) don't charge for customers using Electron cards.
The (under the counter) response was that the Electron account is comparatively cheap for banks to administer because the card is generally provided to people who have difficulty getting an ordinary current account. The rules applied to most, but not all customers are simple - no overdrafts or credit but it means that such folk can use their cards to buy on line or electronically at retail outlets.
The banks charges to retailers for using Electron vary according to what other volume of business the retailer gives the bank using other cards, in Ryanair's case, (and other such large companies) it's not beyond the realms of possibility that the bank don't charge Ryanair anything for accepting Electron.
That said, with the current economic problems being what they are, I was told that if the volume of Electron business adversly affected other credit/charge card profit, they'd have no option to charge retailers and those charges would be passed on to customers.