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.
I think everyone agrees that it might be slightly unfair to take payments for assessments but surely this cannot be enough to turn someone off the job! Successful candidates essentially have their career laid out for them; a reasonably secure, well-paying position with a pension and great prospects for career progression, not to mention the opportunity to fly an airliner, which is what we all want! Perhaps a couple of hundred euros is a small price to pay for the potential returns...