I think the current airport duopoly doesn't help with that though.
There is a perception (with good reason) that any new entrant will provoke a reaction from either Aer Lingus or Ryanair.
But yet, routes that are more dependent on inbound than outbound tourists don't interest them as it provides marketing hassle. This is espacially true in the case of Aer Lingus. One advert can tell people a whole array of places that Aer Lingus fly from Cork. Should they launch a route like Dusseldorf, they spend the same amount for a route that may only be flown 2 or 3 times a week.
I'm a bit doubtful about the claims of Ireland being an expensive destination. It's probably true of the restaurant sector, but the price of attractions and so on are competitive and our hotels now offer some of the best value for money in Europe (on a recent business trip to Dublin I spent E52 per night on a decent 3*, in February, I spent E27.50 pppn for a B&B rate at a 4* in Sligo).
I think there are two things that have been killing our tourism from overseas - a lack of infratructure for independent travellers and also after lower emigration from 1990 to 2008 fewer Irish returning to take holidays at home. I guess the second one won't be a problem for much longer though.