Well my Storm2 is 4 months old, just sold it for R2200, the best offer i could get on it.
The 9700 is the same value new, so best case you may get R3000 if its still reasonably new, but if its an old handset, past 18 months then your better of just giving it to a friend or family member who needs to join the ranks of the Berryers. LOL
Will lose value fast because the 9800 is out. Don't buy it for more than R2500-R3000. Only buy a Blackberry if you really need the BIS. You will probably get R1000 - R1250 for the phone in 2 years time.