3 reasons usually cited for price differentials such as this:
- vat higher by 3.5% in ROI
- wages (esp minimum wage) higher in ROI
- currency differences
I'm not saying these are necessarily valid in this particular instance but on the face of it, they do appear reasonable at least in theory.
If there really is profiteering or rip-off in relation to UK prices translating to Irish prices, I would have thought that normal competition in the market would have eliminated it, at least in part - for example if all furniture store chains are enjoying higher margins in ROI than in NI, one chain would be tempted to cut their prices to gain market advantage. Same goes for chemists, supermarkets, diy, bookstores and plenty of other sectors, even coffee shops such as Starbucks. The fact that the price differential spreads over all these sectors, and I can't think of any company that has chosen not to apply it, even price-sensitive businesses such as Lidl. This leads me to suspect that the reasons behind it are genuine.