I don't get the secrecy. Why don't you tell us your route instead of referring to "A-B"? We may come up with alternatives. Maybe there is an airport very close to either "A" or "B" that is served by a low cost airline.
Also, sometimes the construction of a partial open jaw, i.e. A-B-C, B-A will save a lot of money compared to A-B, B-A.