Tony,

I looked into that trip to Aus when looking for my GT. In the end I decided (for me) that the Seychelles was the correct trip. Most of the fishing they do off that trip in Aus is from the boats. Not much wading and that is what I was looking to do to get my GT. As for the airfare I think others have addressed that adquately.
Here's the bottom line. When you are talking 10K or 15K for a true bucket list. If the 15K is really the trip you want to take then IMO its a mistake to take the 10K trip, especially if its a trip you are only going to do once.

Steve