Originally Posted by xliioper

The article is misleading. It was not actually different fares for the exact same flights. When doing a roundtrip search delta.com shows lowest "possible" total roundtrip fare rather than each-way fares. They were using different search algorithms when logged in and the fare search would find some alternative broken fare options for return flights leading to lower "possible" roundtrip flight. When looking at prices, they were only looking at outbound flight listings and did not go beyond that to see the what return flights the total price was based upon. The fare being quoted for the outbound flight was actually exactly the same in both cases when people actually investigated it further (there's a thread here somewhere on the issue). The lower total price showing when not logged in required booking a connecting broken fare option for the return (while the higher prices were for returns on a single fare component -- generally non-stop).