This is largely a question of Guinness being able to dictate price to the publicans. Due to their complete hegemony over the Irish drinks trade they can basically charge whatever they like, no pub is going to risk taking Guinness off and Guinness knows it.
The issue then is the publicans can either chose to pass the increase on to the public, which they have been doing for time immemorial, (and usually with a bit on the top for themselves). Unfortunately for the humble publican the pub trade aint what it used to be and they're slowly coming to terms with the fact that a lot of consumers are voting with their feet and staying away due to high prices. Which leaves them in a dilemma, they can go down the traditional route of passing on any increase in price from their supplier or they can absorb the cost from their margins.
Which is a rock and a hard place situation for the publican, if they jack up the price do they see another few customers make alternative arrangements with a trip to the offie, or do they see the amount they make on each pint decline by a few cent now and maybe a few cent more when the budget comes out next month?
There's been a paradigm shift in the behaviour of a lot of consumers in relation to pub-going and it has been almost wholly to the detriment of the publicans and it is a bitter pill to swallow, and one which they're not used to. Which is why we're hearing such discontented rumblings from them on the issue.
Either that or it's the fact that they're all a bunch of argumentative types down in Cork.