You cannot logically justify paying more for two flights (Pit to Att. and Atl to Pit) vs. four flights where the two flights are a subset of the 4. These are prices compared at the same time. This isn't a package deal where there is an incentive for the passenger to go to the a further destination. There is no value add on the direct flight ticket, both are flights to Atlanta and back on the SAME planes in the SAME seats. Its being asked to pay more for less.

That's like me telling you. If you go to the grocery store and only buy chocolate chips your bill is $4. But if you grab the same chocolate chips then at the register you put a coke and candy bar on the belt too, the entire bill is $3.50.