You can get an import permit from Department of Agriculture in Pretoria for only R 160.00.
The problem is, you also need a health certificate from the importing country issued by their government. That is normally arranged by an agent in that country and the costs varies from country to country and from agent to agent and depends on the amount of fish.
You alo need to clear the fish through a clearing agent in South Africa to clear the fish through customs, and they are going to charge you a few thousand depending on who you employ and the value.
The most breeders abroad will only work through an agent and will not sell directly to you.
Most breeders will also only send a minimum of 15 boxes of fish that will cost you at least 100k
Then you also need an importers code which you will get from the Receiver of Revenue after you register as an importer and will not costs you anything, except the hassles to get a code.
The freight charges are about R 3000.00 per box depending on the quantity and airline.
There is no symple answer. It all depends on the circumstances.