Other Middle East and Africa Frequent Flyer Programs - SAA price on Expedia lower than on SAA

Hi all;

Looking to book CPT/MQP/LVI/JNB on SAA for next June. Expedia comes out $100 less at todays exchange rate (6194 ZAR vs. $685 ) than direct booking on SAA.

Any ideas? Could Expedia be using an old exchange rate. If so, I think it's to my benefit.

Thanks in advance.