Well hello, I’m a Brit living in USA and I pond hop a few times a year, so I’m straddling this issue a few times.
In general in the case of Anker I found their prices on par with the average exchange rate for the products which are electrically country neutral (batteries, cables), so there was no sign of “Milk the Brits” (unlike others). True, the choice was more limited and as you say less promotions - although I note the little competition in this forum includes the UK (go win!).
I agree that if you exclude the promotion offers, Anker is not the lowest cost. I rarely buy much from Anker other than promotions for that reason.
I have this last year or so bought 2 Anker products in the UK, the UK version of the Powerport2 which is physically very tied to the UK plug type and the Powercore 1000 as I needed it urgently for internal UK trip needs and I checked and UK prices were identical basically so no need to rush to buy from within US to pay extra for postage.
FWIW I wanted to get more USB-C multi-port chargers and this year I bought a Choetech 6-port dual USB-C in UK as it was cheaper than in USA and I wanted another UK power cord (the type which plug into laptop and Anker Powerport5) as those cables are often more reliable than country plug adapters). Anker doesn’t make such a thing, and it is here, now, by my bed in California. Anker be shamed.