I would be very curious how he ran the numbers...free planes mean no capital cost...unless he had to buy engines, which you didn't mention, so we are basically talking about a crew, a mechanic and fuel in Africa...$7000/hr? Now I don't fly in Africa, but are you telling me most of Africa even has noise abatement?
Reminds of a friend who got his boss into a GIV..he was running the numbers this way and that for the board...basically he fudged some 'seat per nautical mile' numbers to make it look like loading up 15 people in a Gulfstream beat the airlines flying coach...the company folded a few years later...
All that said...it sounds like the NGO just couldn't afford the gas and pilots even if they had free planes..
I'll take the Gulfstreams...PM me....