It's not entirely that simple - if there's a store branded price on the shelf or a sticker, that takes precedence over any MSRP printed on the product itself by the manufacturer. Otherwise people could just rip off store branded stickers and opt out of the store's markup.

Maybe it's just not become an issue since the MSRP on most product packaging here is in £ or $ as they just reuse the UK or sometimes US packaging so it's clear that price is not aimed at Irish consumers.