I can't read this, but I have to comment anyways. My guess is simply that america has two times the gdp per capita of the UK. Even if the cost of labour in boston is equivalent to that of london, that isn't going to be true elsewhere. the pre-made sandwhiches are most likely not made in Boston or London (rather cheaper towns in the same area). Because the average american is so much more expensive, the only surprise is that the difference is only 2 USD.