OK it is off thread (who cares, apart from some early stuff about Greece, it has been for ages!) and I'm not here to bash 'em - I use them all the time and when I book early they are usually very very good value on Ireland-UK routes.
But this short change trick has being going on for years. They attempted to do it to me twice (last time 3 quid change owed which I had to ask for twice and finally begrudgingly received as I departed the a/c - I wasn't leaving - that's the price of a pint!) and from now on never order anything in-flight unless about to actually die from starvation or thirst.
It's not just me, many friends have reported same thing.
But is there a law of diminishing returns regarding this type of behaviour?