It certainly pays to compare customs brokers, as the fees can vary considerably.
Also another tip David make sure you clean your aircraft well before you pack/ship. I had one aircraft a few years ago that had some mud & grass on one of its wheels, and the quarantine nazis required the aircraft to be cleaned and decontaminated. They had a contractor unpack my container and steam clean the aircraft. They must have used a large industrial steam cleaner as they did quite considerable damage to the aircraft. And we were charged over $2K for the privilege.