I have noticed the same thing. What I do for a circle trip is:

1) look up the three lowest base fares that allow for my advance purchase and day/time restriction and then add the taxes. If the total price displayed for the circle trip with the flights I like is what I just calculated, then I know I have the lowest possible fare for the circle trip.

2) If the price displayed is higher, meaning seat availability is the limiting factor, then I ask for a round trip on the three city pairs. Sometimes Expedia will find a cheaper routing, and then I specifically ask for that routing on the circle trip.

I am guessing that the additional time Expedia will spend looking for cheaper routings is used only on round trips (or an open jaw, which is basically the same thing), but not on a circle trip, because the number of possible routings increases dramatically as you add stops.


If you know what flights you want and are having trouble getting Expedia to display them because they're $2 more, go back and set up a multi-city itinerary using the connecting city as a "stop". This will cancel the complicated routings that are done on round trips.

When you choose flights, ignore the initial price estimate because that is estimated assuming that each entry in the multi-city itinerary is an individual fare. Once you choose flights, assuming you have chosen appropriate connecting times (less than four hours domestically), Expedia will re-calculate the price using through fares.