The penny (or less) on the dollar these third party sites provide in exchange for using them is completely not worth 1 phone call you have to make to them for changes and cancellations.

Having said that, I did find a West Coast-Japan fare on Priceline (published side, not opaque) that had the exact same flights, fare class, everything - even the same fare basis, which displayed when you loaded the fare rules) a few years back.

I filed a claim via Delta’s low fare guarantee. They refunded my card the difference between their fare and the fare PL had, and also provided the $100 certificate that comes with the terms of the guarantee.

But every other time, the fares have been identical, for the exact same itinerary and booking classes.

Yes, there have been “special fares” on Expedia, but these are a different fare basis, class, or have different restrictions in the fare rules, which make them not comparable.