Timewise, after Eindhoven the closest airport to me is Weeze and it's not far away. Girona or Reus are not thát far from Barcelona either. If I can get there for one cent, the 30 euros or so for transport to the city and thus more or less the only costs involved are not really high. Okay, Amsterdam-Barcelona instead of Weeze-Girona would save me maybe an hour each way, but that's not a lot of time, is it?
But I always count all the transport costs involved and usually during the summer, an airline like Lufthansa is cheaper and better. Most of my Ryanair flight are purely flown by me because they are so cheap that it's more expensive to stay home. The average ticket price I've paid with Ryanair must be somewhere well below 10 euros all-in.