It may have a large part to do with where in the UK you were coming from, and where in the US you wound up, in fairness. Bog-standard eggs are $8/dozen just outside a major metro on the East Coast, while less than half that for posters in other regions. Last week, I was in Manchester, and a 15-pack of eggs at the Lidl on Piccadily Gardens was about £3 or so, which would probably make $8/dozen seem pretty crazy in comparison. I think the lowest I saw while there, further from the city center, was £2.15 for 15 eggs.