VAT and duty are a hit and miss. Most times the waybill devalues the items and vague description. i.e. gadget US$10. The PostOffice charges a very small handling fee wheres TNT will charge a lot. I have had to pay the PostOffice a total of R65 (duty + handling fee) for a R1800 item and TNT not a cent for a R3000 phone.
Often if you order multiple items they are shipped independently if the site sells direct.
Some sites are escrow sites. They collect payment on behalf of the sellers. They only pay seller once item is received and they act a negotiator if there are problems (i.e. Chinavasion, DinoDirect). Other sites offer insurance again non delivery (i.e. GeekBuying) For a R2K phone its less than R25.