Is it possible that the WT Society is also getting some money out of this arrangement?
Not money, but free trips worth 10's of thousands of dollars.
In exchange for a promise of X number of persons booking the (somewhat overpriced) tours with their company, WCS will provide Y number of free trips for "the elite".
Bethel heavies and their wives will get the free trips.
That's pretty standard with any travel agency - if you book a group on a tour, the travel agency will throw in a free package for the organizer. The Society is organizing a group of several hundred, maybe a few thousand, tours for the conventions, so they probably get several dozen free packages.
$4500 per person for probably 10-14 days in South Africa is probably about right - that's going to include airfare, all transportation & lodging, and probably 3/4 or so of the meals, plus probably several "non-theocratic" excursions - maybe a mini-safari, maybe a city tour or 2, etc.