Fedex Express - Ridiculous Import Fees

I have an import from overseas which value is R4929. Fedex sent me an invoice for R2189.07 for duty and processing. That's almost HALF of the value of the import. Either they are ripping me off or they clearly used the wrong tariff heading. I tried Fedex now for the first time after using DHL Express for years. DHL charged me approximately R1350 for a R7200 import. Where does FedEx get their calculations from???? Very disappointed first time customer.