But it is a rather interesting question - why would goods bought in bulk at cost price be very much more expensive than the same goods bought at full price from abroad? Do British retailers charge a huge mark-up? They certainly do when they sell their goods in Ireland - there are regularly outraged articles in Irish papers where people have peeled off a euro price on goods in British chain stores in Ireland and discovered a far cheaper pound price underneath, far, far less than would be justified by the exchange rate plus extra Irish VAT.

The same happens in Britain, just taking one retailer where I can speak from experience.
Tesco have different sized stores in Cardiff, and the prices for produce, and even branded foodstuffs vary in each of the three store sizes. This is presumably based on the cost of operating the various stores, Logistics, Customer/staff ratio, ground rent, etc.
Why should there not be further differences with extended supply lines into a different country, and different rates of VAT?