Wildly inconsistent Pepsi prices

A couple of days ago I was thirsty, so I went to the nearest convenience store with my X-treme Gulp 52-oz insulated beverage mug, and filled it with Pepsi for about 99¢. Personally, I was expecting to pay less for a refill, especially since 52 oz is around 1.5L, and a 2L bottle of Pepsi cost 89¢ at the store last time I was there. So today I went to the store, and found that 2L Pepsi was on sale for 78¢, so I bought 2 of them. At the register, I noticed in the little refrigerated section they had some 20-oz bottles of Pepsi. Now, I've long known that 1L bottles of soda generally are priced nonsensically higher than 2L bottles, but the 20-oz bottles are much smaller -- only 0.6L...and yet they were selling these 0.6L bottles of Pepsi for $1.80, in the same store where they were selling 2L bottles for 78¢. I got 4L of Pepsi for less than the cost of 0.6L.

It has to be the refrigeration. I never see 2L bottles in the refrigerated section. So the extra cost must be because it's cold. Of course, this doesn't explain how sometimes I see Dasani or Aqua Vita being sold for more than the same size of Pepsi or Coke. It's the same filtered water as they use in their sodas, just without the syrup and carbonation -- and they price it higher for this.