I used to use Hipmunk, but at this point, I’ve built up a lot of airline loyalty and often find booking directly with the carrier or through a credit card portal (if I’m using points) for personal travel gives me the best fare. All my business travel has to go through Concur anyway, so search tools like Hipmunk and Kayak don’t matter, no matter how nice the interface. When I didn’t fly all the time, I didn’t care abo…
I think for corporate travel management, the fee structure is usually $X per transaction, rather than a percentage of the fare, although I can't speak to exactly how Concur charges, and it'll differ depending on the size of the customer. Average ticket prices for corporate airfare are likely considerably higher than for consumer, since that's where the majority of business class and refundable tickets are sold.