I hate to knock HDEW ... but I think we all know that something doesn't add up......
I have a partial or potential answer to this. If you take the street price of said item A from New York or Hong Kong, it is 1500USD. Same item from the same production line will be sold in the UK from official sources for 1500GBP, of which 1252GBP is the landed price but with 4.2% import tax and £1246 without import tax. Using 1.55USD to 1 GBP, you can see the street price in NYK or HKG is £967. Add £25 for UPS/DHL. You can see there is a profit to be made whilst complying with UK tax obligations.
Well there clearly *would* be an opportunity to profit *if* the US/UK prices were as you surmised ($1500 and £1500), but in reality they usually[*] aren't.
Let's look at a real life example. I like to use the Canon 70-200mm f/2.8 IS Mk II as a benchmark, because it has a lot of desirable properties:
* it was introduced several years ago, so there are no longer any 'early adopter' premiums being charged:
* it's not being replaced imminently, so you don't have retailers trying to shift surplus stock;
* it's not sold as part of a Canon kit, so there isn't a 'white box' option to confuse the pricing;
* it's a professional lens so it isn't packaged into any bundles by retailers which again could confuse the pricing;
* it's very very popular, so all half-decent retailers will stock it.
Currently at B&H in New York this lens sells for US$1999. Today's exchange rate is £1=$1.5519, so the B&H price is £1288. Add on 6.7% import duty and you have £1374. Add on 20% VAT and you have £1648. And yet all the major UK retailers, including Amazon, are selling this lens for £1499.
And HDEW are selling it for £1275. Draw your own conclusions. My conclusions are that (i) the UK market is much more competitive than the US market, so the margins are lower; and (ii) there is no way HDEW's price can possibly include import duty and VAT. What are yours?
[*] There is one situation where UK prices are routinely out of step with other countries such as the US and HK, and that is when new products are introduced. UK retailers tend to charge an 'early adopter' premium, so we do see the situation where the initial prices are $1500 and £1500. But the differential usually goes away within 3-6 months.