The problem here is this:
If I were to go to 3 of the 7-11s within driving distance, I would get approximately 21.33 oz of Slurpee tastiness.
This would be free, if you don't count the approximate 4-5 dollars in gas I would be using.
If I went to the nearest 7-11, a few miles from my house, I'd use less than a dollar in gas, and get my regular 40 oz Slurpee, which I have no problem finishing, for $1.59, plus tax.
Great deal.