Ryanair were *FORCED* to take the step of flying to airportts people wanted to go to on the terms of the airports themselves as they ran out of minor airports to steamroller. Look at EDI, BAA Airport, spending millions on the Terminal, you can be sure as Hell that Ryanair got a good deal but NOT a freeby.
Hence the full service passengers don't subsidise the Ryanair passengers and
FR have to pay a market rate to use the facilities. Any introductory offer is for an inital period only. This is a major shift in their business model, only time will tell where it will pan out.