For one thing, you are going during the high season ( June, July, August) tickets are always more expensive. The 2000.00 is reasonable, my ticket for this August is 2300.00 (S.D. to Joburg then to Windhoek) and I checked many travel agents. Sometimes the earlier you get your ticket the better. The consolidators still have specials, when they are gone the price goes up.
I don't use the computer sites for flights, I like to have a direct contact with a live agent incase a problems arises, and I have that. I am one of the unlucky ones to not draw a Leopard permit for 09. I was to hunt this August in SA and Namibia. This would of been my third trip and the only one I did not buy hunt insurance. Don't forget that.
Good luck on your trip, it will be a blast.