It really bothers me - against what I know of economics - that given the fact I don't have a car, I am occasionally constrained to pay $3.99 at the corner store for a gallon (3.78L, for those of us lucky enough to live in saner places) of milk, when those with cars can purchase the same gallon for $2.62 at the Wal-mart, less than three miles distant. My transport costs are usually higher than the differential, so I'm maximizing utility accordingly, but it still bothers me. Further, the chocolate costs about 30% more than the white, regardless of store. I can't explain that, either.
The real kicker is, of course, that a gallon of milk back home costs about $6.60.