It’s also a mistake to assume that the cost of products in brick-and-mortar outlets will correspond well to the marginal cost of the product as reflected in the exchange rate. The fixed cost (Rents, utilities, licenses, bribes, labor) of a retail outlet are significant [else you could simply start your own store, and buy wholesale, couldn’t you?, highly localized even within a specific region (upscale downtown vs. suburban vs. rural strip mall) and not at all comparable to overseas internet operations, some of which drop-shipp from a distributor warehouse, and are little more than order-taking operations.
All that is standard economics. What is sometimes lost in the shuffle is: every piddling object used in the operation of the store is subject to the same sort of “UK tax” that you’re (and my UK friends) complaining of, from the giant bulbs in the fixtures to the barcode scanners – even if the product is made locally. A British bulb manufacturer will ask what the competing French or American (or British) product costs, weigh benefits and quality, and price accordingly. “Marginal cost + X%” doesn’t enter into it (unless X is too low to be appealing)
IMHO, almost all product prices come down to competition. That’s hardly a revelation, yet I constantly hear (in daily life) analyses that pretend prices hinge (or should hinge) on “cost+X%”, which results in countless paradoxes, all of which, all too often devolve into rants about 9e.g.) how the system is “fixed”.
There’s also a "hassle factor.’ Many companues, especially initially, consider overseas sales to be a hassle - shipping, taxes, customs, legal uncertainties like local liability laws, fraud, local packaging and quality requirements, currency fluctuations for items priced in overseas units, etc. – all subject to change at the whim of an ‘unknown’ foreign government or international events. It doesn’t matter if those hassles and costs are significant or even correct. All that matters is the perception in the eyes of the seller – i.e. how much profit it’d take to make them undertake the percieved risk.
You might say “That’s not a hassle, that’s their business!” Yes, but it’s still up to them how much markup they feel makes it worthwhile to add overseas business - your purchases aren’t any more expensive because a couple of yahoos in East Dakota, USA want a $100 premium for ‘all that hassle’ when it’s actually minimal. You can find some outrageous price on almost any item, in almost any market. You simply don’t buy from those sellers, so who cares?
It works in reverse too: a buyer can usually find far better prices on the internet than in their local market (eliminating much of the OPs complaint) but they often prefer the convenience of the B+M: the ability to try on jeans, ease of return without international postage, etc. These factors often parallel the risks and hassles that the seller would undertake. Many buyers want sellers to undertake the hassle for them (as well as hassles that wouldn’t apply to a buyer), at a price comparable to a domestic sale without the hassles
There’s a lot of “should” in economics. Actually, there’s very little ‘should’ in the operation of the market, it’s all in the discussions.
It all comes down to: why would a UK seller charge less than they do? If a competing seller could easily offer lower prices, it’d be a tremendous business opportunity - but I think you intuit that it’d be “more hassle than it was worth”. Clearly, that isn’t happening locally, and overseas sellers apparently aren’t strenuous enough competition, due to buyer preferences.
We can change that balkance ourselves. Buy on the Internet. I have UK friends who get a significant fraction of their purchases, even nonperishable staple goods, from US websites, and a major fraction of my US purchases are on the web, not local. If the difference in cost and hassle is truly insufficient to justify the price differential, do an end run about it. Importing the goods yourself (e.g. buy on Amazon.com or amazon.ca rather than amazon.uk) Don’t wait for someone to offer you that product at some price they’d be happier for you to pay