As Spin mentioned, all the kids I know who have gone on trips like this have raised most of the money themselves through car boot sales, car washing etc. Usually there is an 18 month period to do this. Their trips were a similar price and the trips to E Africa and Borneo were really excellent.
My daughter did a Biology expedition to Dominica which was much less (2K), but raised most of the money through baby sitting and selling raffle tickets.