I have a few pals at work (here in London) from Westport and they will often fly to Knock, but come home from SNN or DUB as they say "You have to pay extra to fly from Knock".
Sorry that's the daftest thing I've ever heard. By booking 2 separate flights they would have had to pay double the credit card charges, not to mention additional transport costs and hassle. cost.
Are you sure it wasn't down to lack of late flights to get back to UK for work they chose SNN / DUB for services? Sounds more plausible.
How much of a detriment do we think the departure tax has?
Interesting question, I think it's polarising and does have a negative impact. Very often people don't look past headline fare and just see it as additional cost. Many are happy, some eager even to support a great local service. But clearly, others find this model of a gate fee galling, even if they'd pay it through ticket fees elsewhere.