Distance have nothing to do with ticket price
I was looking around for air tickets, In West Jet's site, on my return flight, if I fly from Calgary to Edmonton then to Phoenix, I will pay less. But, Edmonton is north of Calgary
I know some of it has to do with the popularity of the cities you fly between.
Now with the oil boom, there are direct flights between Houston and Grand Junction again. The direct flights are about $80 more than the 1 stop flights. (changing planes in Dallas)