My assumption - not truth, mind you, just the way I've thought about it is this. European airports have a lot of "common use" stations - a Ryanair check-in station can be used for EasyJet a couple hours later, depending on who is flying and when. I believe that in Spain, Aena staffs all the ticket counters as well, not the airline directly. Other countries may or may not have something similar. Either way, that station costs money - not necessarily the $.10 boarding pass, but the space rented from the airport to print the pass and the manpower to run it. RyanAir hates that. They try to be as no-frills as possible. If it's cheaper for them for a customer to show up, completely ignore the ticket counter, and have their only interaction with a human being staff be scanning their boarding pass before they get on the plane (and I'm sure they're looking for a way to get rid of *that*).

By charging an insane amount for printing a boarding pass at the airport, it totally changes the passengers' line of thinking. They don't want to pay those fees. Their hostel probably has a computer for public use, so they'll gladly sit at that for 15 minutes to save enough money to stay somewhere for a few days. Which is exactly what Ryanair prefers. Then, since their ticket counter is practically deserted, they can reduce the number of "stalls" they have significantly, and they just saved a good chunk of change.

Oh, and one other thing. Unlike airlines around here, Ryanair allows you to check in 2 weeks in advance.