I have spent quite some time researching the cost of weekly food shopping items, building materials, car parts & other items available on the internet(practically everything really) & comparing them with the same or very similar in the UK & other E.U. countries.
Many items here are extremely expensive in comparison to the UK; Royal Canin dog food is 50% more expensive here, it's a French made product! Thus I buy mine from the UK.
I order my tyres for both cars from the UK as they are so much cheaper, even with delivery costs, same with car parts for my Landrover & Peugeot.
I have made comparisons with online companies, comparing ebay.fr against the UK & Germany, always cheaper elsewhere. Compare books on Amazon, there's no competition, we buy elsewhere all of the time.
After all, isn't that what the E.U. is all about, breaking down the barriers between member countries in order to benefit from the economic market, making it easier to trade between member countries?