[sliverstorm]

You can get 2 liters of soda for 99c, and a 12 oz bottle for 1.50

Usually it's $1.50 for a chilled 12 oz bottle, and $0.99 for a warm 2 liter. It's a convenience charge.

[thwarted]

Convenience also in that few people want to consume 2 liters at one sitting, so not having a left over, partially filled 2 liter that you have to look after until you get to a place where it can be stored is often worth the addition 50¢.

[sliverstorm]

Let's not forget the convenience of not having 2 liters tempting you.