My sis (my real one ...is the family know it all on like everything under the sun especially online everything) so lemme try and think like her for a sec (and be 250% anal retentive ...God loves her and expects me too as well )
I believe the way she goes about it is to deal directly with the airlines websites directly. Folowed next by the litany of discounters ..priceln ..xpdia .. et al.
but overall I would tend to think but am not altogether certain (cuz I more often than not get to fly 4 free) that the airlines might (and the fine print would dictate this) reimburse you the difference if you bought and then the price dropped. maybe not though.
nice to see that there are other who go out of there mind trying to save what amounts to small amounts of $$ ..haha
)