I think this is a great idea, and it would be a no-brainer for me to pay if you only charged when you save me money.<p>I think customers (thinking of myself) have a huge aversion to paying money for nothing, in the event there isn't a better deal. If there's any chance I am going to pay for a service that returns no value, I am going to be hesitant.<p>Part of the problem is I didn't see any "success rate" metric, so I don't know what my chances are of saving money. If you knew it was almost 100% given enough days before the trip - then you could even give someone a money-back guarantee, which would kill the "pay money for nothing" objection as well.