Diet Coke

Now, I promise you, this really isn't interesting to anybody but me. I know this because I've told people before and I've marvelled at their lack of effort to even try and look interested.
For years now I've had a bit of a Diet Coke addiction. I try to make this sound more exciting than it is by saying things like 'I'm fighting the coke,' 'I'm a coke addict,' etc etc.
Now what fascinates me is that I can buy a 2 litre bottle of coke (yes not the medium big one but the real big one) for £1. And yet a 500ml bottle (yes those pixie little things) costs £1.15.
See, I told you! It really isn't interesting to anybody but me!!!