I have never had to pay excess luggage fees. But I have had a "discussion" with the person at the checkout counter at times.

Coming back from Namibia in '05, my hunting companion and I had a total of 88kg of luggage (3 guns, camera gear and wooden curios). The lady at the checkout counter was at first insistant that we pay extra. But with some eye fluttering mixed with puppy dog eyes we managed to get out of it. However, my pelican case with 2 guns didn't arrive when we did. It turned up several days later.

Since then we have tried much harder to keep the weight down, but this is very difficult for a 6-8 week stay. Especially with with a couple of guns and a lot of camera equipment.