With the greatest of respect, it's probably best you didn't apply with that level of commitment.
There is, in my opinion, a fine line between "commitment" and being taken advantage of. I can't think of any other mainstream industries where candidates have to pay specifically for a job interview with a company. I have in the past attended one assessment day with an airline where there was an "assessment fee", I subsequently decided it was rubbish value for money.
Good on Aer Lingus if mask14 is indeed correct.