Government fares are often high, especially for routes where there isn't competition, although the tickets are more flexible and unrestricted than published fares.

Maybe this (plus cargo) makes the route profitable as I wouldn't expect people from the Philippines who live in the USA to pay a premium to fly DL for visits home versus one of the Philippines based carriers (I'm not sure whether more than one fly TPAC from MNL, plus there would be some connections through various airports in Asia, although transit now is problematic).