Not sure if it applies to this particular one, but there are a lot of pricing quirks in international, multi-airline itineraries that one can exploit: airline fare rules are fairly complex lists of requirements/exclusion/combination/stopover rules etc., and the combinatorial complexity and ancient IT infrastructure it's all coded in sometimes produces results the airlines might not have intended had they realized it. Particularly lucrative combinations tend to get shut down once airlines notice them, so there's sort of an ethos of not talking about them openly in public. One exploit that was going around for a while, for example, was that certain combinations of cities/airlines would result in the fuel surcharge not showing up on a fare like you'd expect it to ("fuel dumping"); you could sometimes purposely add weird legs to make that situation come about, but weren't supposed to publicly post such a leg if you found one, lest it go away.