I consider 2p one way to be free. There's probably some law or contractual reason (maybe just marketing) why they have to charge something.
If we wanted to return on a different date we could have returned for just 2 (irish) pence.
no miles though.......(although I did get 40 UA Mileage plus miles for our trip using my mileage plus visa !!!

)
The Jury's out (irish hotel pun not intended) in whether airline tax should be a percentage of fares as opposed to the flat rates currently charged.....now that would put the cat amongst the pigeons.....