Yesterday I bought a "Bacon double cheese XL burger" meal*, which is £6.99, plus 60p to 'supersize' it, in other words get a few extra chips and a drinks cup the size of a bucket.
It wasn't really enough, so today I just got two of their £3.79 "Big King" meals, as a result I got a lot more food (four burgers and even more chips) for one penny less. The lass behind the counter happily swapped the two normal sized cups for a bucket-sized one.
Strange. You'd expect the reverse to apply.
* Off limits for Hindus, Jews and Muslims!