The psychology of marketing, innit. The same reason Tesco marks stuff up as 9.99 rather than 10 euro, a peripheral part of your mind sees it as some kind of saving even though when you think about it you just end up with a pocket full of useless pennies and still paid over the odds for your Ribena. Of course you could probably go to Eurocity and get 2 for 5 euro but you're taking a chance there, most of their products are no-name Chinese junk with no reviews, ripped off marketing strategies, dubious origins and ingredients, over-inflated claims, possibly fake photos, and at the end of the day questionable value.
In conclusion, Eurocity needs some kind of forum where shoppers can PM each other to ask for advice before parting with their hard earned euros for shoddy Chinese Ribena.
Wait ... what was the question again?